# CalcTape Web – Manual & Guide

> Manual for CalcTape Web: interface, calculating with comments, user keys, sharing via link and privacy — right in your browser.

- Language: English
- This page as HTML: https://www.calctape.com/en/manual-web
- Updated: 2026-09-05

CalcTape Web is the browser-based version of the **CalcTape** calculator. Instead
of showing only a single intermediate result like a conventional calculator,
CalcTape works like a **paper tape with a notepad function**: you write your
calculation line by line, can add a comment to every value, and edit anything at
any time. Everything is recalculated instantly.

> *Calculate, Comment, Correct:* in your browser, no installation required.
> Your data stays local on your device.

![CalcTape Web in your browser](https://www.calctape.com/img/manuals/web-overview-en-light.webp)

## 1. The Concept: How CalcTape Works

CalcTape differs from a conventional calculator in four ways:

### Line-by-Line Calculation
Each line contains an operator and a value, e.g. `+ 1,350.00`. CalcTape
accumulates the lines continuously, like a receipt.

### Automatic Subtotals
When you close a block (using the **= / Enter** key), CalcTape automatically
draws a separator line and writes the running **subtotal** below it:

```
 +      3,230.00 Salary
 -      1,350.00 Rent
 -        780.00 Groceries
 ---------------
 +      1,100.00 Available
```

### Comments Right Next to the Numbers
You can write any text after a value (in the example above "Salary", "Rent" …).
CalcTape ignores the text when calculating but displays it alongside the numbers,
so every calculation stays easy to follow.

### Edit Anything at Any Time
You can change any value in any line at any time.
**The entire calculation is recalculated instantly.** That is what makes
CalcTape so flexible.

### Multiple Calculations Side by Side
- **Without a blank line** between two blocks you get a convenient **subtotal**.
- **With a blank line** you start a **completely new, independent calculation**
  in the same document.

## 2. Interface Overview

The app is divided into the following areas:

| Area | Position | Function |
|---|---|---|
| **Header** | very top (dark blue) | Menu icon ☰, logo & product name, theme menu, dark mode switch, language selector (globe icon), **"Share"** button |
| **Toolbar** | above the editor | Undo/Redo, lines, typeface, digit grouping, zoom, help (see below) |
| **Editor (tape)** | center, full height | Input area for your calculations (lined "paper") |
| **Status bar** | below the editor | Clickable chips: Zoom, cursor position; errors; "Automatically saved" |
| **Result panel** | top right | Current block result, grand total and memory – each click to copy |
| **Keyboard** | right (mobile: bottom) | Virtual calculator keyboard |
| **Apps panel** | bottom right | Links to the CalcTape apps (Mac, Windows, Android, iPhone, Business) |
| **Footer** | very bottom | Copyright, version, legal links |

### The Header
The **header** spans the very top of the window (the dark blue bar) and gathers
the app's global controls. From left to right it holds:

- the **menu icon (☰)** – opens the main menu with all commands (section 6);
- the **logo and product name** "CalcTape Web";
- the **theme menu** – pick a color palette (see below);
- the **dark-mode switch** (moon/sun icon);
- the **language selector** (globe icon);
- the **"Share"** button – create a share link or save the calculation
  (section 8).

![The header](https://www.calctape.com/img/manuals/web-header-en-light.webp)

**Color theme.** The **theme icon** (a half-filled circle with a small arrow)
opens a menu with several color palettes:

- **Standard** – the classic CalcTape look (navy/blue).
- **Modern** – a bold indigo/slate scheme with colored key accents.
- **Subtle Slate** – a calm, muted steel-blue for relaxed work.

The palette is **independent** of light/dark mode: any palette can be combined
with the light or dark theme.

**Dark mode.** The **moon/sun icon** switches between light and dark themes. On
the first visit CalcTape follows your device's system setting; your choice is
then saved.

**Language.** The **globe icon** switches between **Deutsch**, **English**,
**Español**, **Français**, **Italiano**, **Português** and **हिन्दी** (Hindi);
the active language is marked with ✓ and is saved. Without an explicit choice
CalcTape follows your browser's language. This manual is available in all of
these languages too.

Your palette, dark-mode and language choices are all stored locally and restored
on your next visit.

### The Toolbar
The most important actions are available as icon buttons directly above the tape,
organized in groups:

- **Edit:** Undo, Redo (grayed out when not available)
- **View:** lines on/off, proportional typeface, Indian digit grouping, zoom out,
  zoom display (click = reset), zoom in
- **Help:** opens a small menu with two example texts ("Getting started",
  "Working with variables") and the link to this manual

![The toolbar](https://www.calctape.com/img/manuals/web-toolbar-en-light.webp)

**Save calculation** lives in the **Share** popover (section 8), not in the
toolbar.

Each icon shows a tooltip with a plain-text label **and** keyboard shortcut on
hover (e.g. "Undo (Ctrl+Z)").

### The Result Panel
The **result of the current block** is displayed large and clearly in the top
right. **Clicking the value copies it to the clipboard** (brief confirmation
"Result copied"). Below it, two rows show the **grand total** (the sum of the
final totals of all completed blocks) and the **memory value**; each can be
copied with a click. The small **copy icon** next to a value indicates this.

![The result panel](https://www.calctape.com/img/manuals/web-result-panel-en-light.webp)

### Adapting to Window Size
The interface is **responsive**:

- **Wide window (desktop):** Editor on the left, result panel and keyboard on
  the right; everything uses the full window height, and the tape scrolls
  internally.
- **Narrow window (mobile):** The keyboard becomes a **bottom sheet** at the
  bottom of the screen, with a drag handle and a mini result in the header.
  Tapping the drag handle collapses and expands the keyboard.
- At very low window heights, the keys are automatically made more compact.

CalcTape can also be added to the home screen on mobile devices as a **PWA**
(Progressive Web App) and launched like a native app. For everyday work on a
phone, the CalcTape apps for Android and iOS are the better choice (section 12).

## 3. The Editor: Writing Calculations

The editor is the heart of the app. You can type freely using a **physical
keyboard** or use the on-screen keyboard buttons; both work equally well.

The tape looks like a **lined notepad** (the lines can be turned off via the
toolbar or Ctrl+L). For orientation, the **line containing the cursor** is
subtly highlighted in blue and marked with a blue bar on the left; all **lines
that are part of a calculation** (values, variables, sum lines) have a continuous
sand-colored stripe on the left. **Totals** are displayed in bold, so the result
of every calculation is easy to spot at a glance.

![A calculation, line by line](https://www.calctape.com/img/manuals/web-editor-en-light.webp)

### Line Structure
```
 <Operator> <Number> <optional comment text>
```
Example: `+ 1,234.50 income March`

- Every calculation must start with a **number** or a **sign** (`+` / `−`).
- Available operators are addition, subtraction, multiplication, division, and
  exponentiation.
- The **decimal and thousands separators** are set automatically according to
  your browser's language (in English: period as decimal separator, comma as
  thousands separator). The menu also offers **Indian digit grouping**
  (lakh/crore, e.g. `10,00,000.00`; see section 6).

### Percentage Calculations
A percentage value is placed **after a number**, e.g. `- 40.00%`. It refers to
the current running subtotal. Example:

```
 +        910.50 Available budget
 -         40.00% | -364.20  Reserves
 ---------------
 +        546.30 Available
```

CalcTape automatically displays the amount calculated from the percentage right after it (in the example `| -364.20`).

> Note: The operator immediately following a percentage value must not have a
> higher precedence than the percentage operator. If a corresponding error
> message appears, insert a subtotal after the percentage value.

![Percentages are calculated automatically](https://www.calctape.com/img/manuals/web-getting-started-en-light.webp)

### Comments
Everything after the number is treated as a comment and does not affect the
calculation. This lets you document what a value represents.

### Variables (Named Values)
CalcTape lets you name values and reuse them later. Variable names must
**start with a letter** and must **not contain special characters**. There are
two ways to define a variable:

**1. Direct assignment: `var = 123`**
The variable name goes **to the left** of the equals sign, the value to the right:

```
 vat = 19
 +      1,000.00 Net
 +           vat% | 190.00  VAT
```

**2. Naming a sum line: `... = var`**
In a **sum line** (subtotal), the name goes **to the right** of the equals sign
and takes on the result of that line:

```
 +      3,230.00 Salary
 -      1,350.00 Rent
 ---------------
 +      1,880.00 = budget

 +        budget
 -         25.00% | -470.00  Savings rate
 ---------------
 +      1,410.00 Available
```

The defined variable (`budget`) can be reused afterwards. In the example, a
new calculation starts after the blank line, takes over the budget and subtracts
a 25 % savings rate. This second form is **only allowed in sum lines**; in all
other lines the variable name must go to the left of `=`.

Further background on variables and advanced calculation rules can be found at
[calctape.com](https://calctape.com/en/).

![Working with named values](https://www.calctape.com/img/manuals/web-variables-en-light.webp)

### Editing, Inserting, Deleting
- Click anywhere and overwrite the value;
  CalcTape recalculates immediately.
- **Paste from clipboard** (Ctrl+V) is supported; if the content no longer
  fits completely, CalcTape offers to insert only the part that still fits
  (line limit, see Section 12).
- **Delete** using the ⌫ (Backspace) or Delete key.

### Error Display
If a line contains an error, it is marked directly on the tape (red left border,
reddish tint, wavy underline); the plain-text description appears as a tooltip on
the line and as a red chip in the status bar (see Section 11).

## 4. The Keyboard: All Keys Explained

There are two slightly different layouts: the **desktop keyboard** (portrait,
right side) additionally has the four memory keys; the **mobile keyboard**
(landscape bottom sheet) omits them for space. The keys are color-coded by
function:

![The on-screen keyboard](https://www.calctape.com/img/manuals/web-keypad-en-light.webp)

### Number Keys
`0`–`9`, the double zero `00`, and the **decimal separator** (period). Use
these to enter values.

### Operator Keys
| Key | Meaning |
|---|---|
| `+` | Addition |
| `−` | Subtraction |
| `×` | Multiplication |
| `÷` | Division |

### Function Keys
| Key | Meaning |
|---|---|
| `= ⁄↲` (Enter) | Close block → calculate result, draw subtotal, new line |
| `%` | Percentage calculation |

### Memory Keys
The four memory keys exist only on the desktop keyboard:

| Key | Meaning |
|---|---|
| `MR` | Memory Recall: retrieve/insert the stored value |
| `M+` | **Add** the current value to memory |
| `M−` | **Subtract** the current value from memory |
| `MC` | Clear memory |

The `MR`, `M+`, and `M−` keys also show a small preview of the affected memory
value, so you can see what the key will do before pressing it.

### Control Keys
| Key | Meaning |
|---|---|
| `AC` | **All Clear**: discard the entire calculation and start over |
| `⌫` | Backspace: delete the last character |

> **Tip:** Accidentally pressed `AC`? Use **Undo** (the icon in the toolbar or
> Ctrl+Z) to restore the previous content, as long as the tab stays open and
> is not reloaded.

### User Keys (VAT)
On the right there are two **customizable keys** for VAT, labeled `+VAT` and
`−VAT` by default. They insert a pre-configured calculation step; the VAT rate
is set automatically based on your locale (in Germany 19 %). These keys can be
freely reconfigured (see the next section).

## 5. Customizing User Keys (VAT)

Each of the two VAT keys has a **gear icon ⚙** in its bottom right corner, which
appears when you hover over the key with your mouse (on touch devices it is
always visible). Clicking it opens the **"Edit user key"** dialog.

### Fields in the Dialog

| Element | Function |
|---|---|
| **Label** | Text displayed on the key (max. 16 characters) |
| **Formula / text** | What is inserted when the key is pressed, e.g. `+ 19%` or `* 0.8` |
| **Calculate / Enter [= ↵]** | Toggle switch (see below) |
| **Default** | Resets all fields to the factory defaults |

### The "Calculate / Enter" Toggle
This switch controls whether a **line break** (equivalent to the `=`/Enter key)
is triggered automatically after the content is inserted:

- **On (default):** The result is calculated immediately after insertion and a
  subtotal is drawn.
- **Off:** Only the formula is inserted; the line stays open so you can keep
  typing.

### "\n" for a Line Break in the Formula
You can write the character sequence `\n` in the **Formula / text** field; it
will be replaced by a real **line break** when inserted. This lets you store
multi-line snippets on a single key.

### Saving & Resetting
- **OK** applies the changes; the new label appears on the key immediately. The
  setting is saved locally and persists.
- **Cancel** discards the changes.
- **Default** refills the fields with the factory values. This only takes effect
  after clicking **OK**; nothing is permanently deleted until then.

## 6. The Menu

Click the **hamburger icon ☰** (top left) to open the main menu. It shows the
corresponding keyboard shortcut next to each entry and contains:

![The menu](https://www.calctape.com/img/manuals/web-menu-en-light.webp)

| Entry | Shortcut | Function |
|---|---|---|
| **Undo** | Ctrl+Z | Undo the last change |
| **Redo** | Ctrl+Y | Redo the undone change |
| **Show lines** | Ctrl+L | Toggle the lined "paper" on/off (on by default) |
| **Proportional typeface** | — | Switches the tape to a proportional typeface (default: monospaced) |
| **Indian digit grouping (lakh/crore)** | — | Thousands grouping in Indian style (e.g. `10,00,000.00`) instead of groups of three; applies immediately to all values |
| **Zoom in** | Ctrl+2 | Increase text/key size (zoom) |
| **Zoom out** | Ctrl+1 | Decrease text/key size (zoom) |
| **Getting started** | — | Inserts an example text with the basics at the top of the tape |
| **Working with variables** | — | Inserts an example text about calculating with variables at the top of the tape |
| **Manual** | — | Opens this manual (new tab) |
| **CalcTape Apps for Desktop & Mobile** | — | Overview of all CalcTape apps (new tab) |

The **Undo** and **Redo** entries appear grayed out when there is nothing to undo
or redo. **Save calculation** is found in the **Share** popover (section 8);
Ctrl+S keeps working everywhere. The memory value and result are no longer shown
in the menu. They have moved to the **result panel** (top right), where they can
be copied with a click.

> The example texts **Getting started** and **Working with variables** (also
> available via the help icon in the toolbar) are the quickest way to get
> familiar with how CalcTape works: they explain CalcTape with small example
> calculations that you can try out directly. They are always inserted at the
> top of the tape; the existing content is kept below.

## 7. The Status Bar

Directly below the editor, the status bar continuously shows the current state
as clickable **chips**:

![The status bar](https://www.calctape.com/img/manuals/web-status-bar-en-light.webp)

| Chip | Meaning |
|---|---|
| **\<%\>** | Current zoom level (100 % = default). Click to reset the zoom. |
| **L \<line\>:\<col\>** | Position of the input cursor |
| **Error** (red) | When there is an error in the current line, the plain-text description appears here |
| **✓ Automatically saved** | Confirmation that the calculation is continuously saved locally |

The **grand total** (sum of all completed blocks) now lives in the result panel
(top right), not in the status bar.

A **warning banner** also appears above the chips when the calculation approaches
the maximum length of 500 lines: from about 95 % it shows a counter
("… of 500 lines"); when the limit is reached it turns red. If a new line is
then rejected, the banner briefly shakes as feedback (details in Section 12).

## 8. Sharing Calculations

CalcTape can share a complete calculation **as a link**, without any server
involvement. The entire content is compressed and written directly into the URL.

### The Share Button
The **"Share"** button is in the top right of the header. It opens a small menu:

- **Save calculation:** Saves the current calculation to a file that can be
  opened with the CalcTape apps (see section 9).
- **Copy link:** Copies a link to the **clipboard** that contains both the web
  address and the complete current calculation (brief confirmation "Link copied!").
  Paste it into an email, for example.
- **System share …** (if supported by the browser, mainly on mobile devices):
  opens the **native share menu** of the operating system.

### Opening a Shared Link

Anyone who opens the link sees your calculation exactly as it was. The following
rules apply:

- **Confirmation prompt:** If the editor already contains something, CalcTape
  asks before loading, because the existing content will be replaced by the
  calculation from the link. Clicking "Cancel" leaves the existing content
  unchanged.
- **The address bar is cleaned up:** After loading, CalcTape removes the data
  from the URL. Reloading the page (F5) does **not** re-import the calculation.
  If you want to keep the link, save it somewhere (for example in a note), not
  as a bookmark of the already-opened tab.
- **Checksum:** Every link contains a checksum. If the link was damaged in
  transit (for example, broken across lines or truncated by an email client),
  CalcTape detects this and shows an error message instead of loading a corrupted
  calculation.

> **Note:** There is no length limit when sharing: any calculation that the
> editor allows (max. 500 lines, Section 12) can also be shared as a link. No
> data is ever transmitted to a server: the content sits after the `#` in the
> address and never leaves the browser.

## 9. Saving and Automatic Backup

### Automatic Local Backup
Your current calculation is **continuously and automatically** saved in your
browser's local storage. Close the tab and come back later; your content will
still be there. Settings (zoom, lines, user keys) are also retained.

### Save as a File
**Save calculation** (Share popover or Ctrl+S) downloads the calculation as a
CalcTape file. You can open this file with the **CalcTape apps**
(Windows, macOS, Android, iOS) and continue working on it there.

## 10. Keyboard Shortcuts

| Shortcut | Function |
|---|---|
| **Ctrl + S** | Save calculation (download file) |
| **Ctrl + Z** | Undo |
| **Ctrl + Y** | Redo |
| **Ctrl + L** | Toggle show lines on/off |
| **Ctrl + 2** | Zoom in |
| **Ctrl + 1** | Zoom out |
| **Enter** / **=** | Close block, calculate result/subtotal |
| **Backspace** ⌫ | Delete character to the left |
| **Delete** | Delete character to the right |

> On a Mac, use **⌘ (Command)** instead of **Ctrl**.

You can also type freely in the editor at any time using a **physical keyboard**
including digits, operators, and text.

## 11. Error Messages

When CalcTape detects an error in a line, it is marked on the line and explained
in the status bar. The most important messages:

| Message | Cause / Remedy |
|---|---|
| **Division by zero** | A division by 0 was attempted. |
| **Too many operators** | Multiple operators without a value in between. |
| **Syntax error** | The line is not formally valid. |
| **Calculations must start with a number or a sign** | Start the line with a valid input (number, `+`, `−`). |
| **Percentage needs a subtotal** | Insert a subtotal after the percentage value (operator precedence). |
| **Percentage only with a simple value** | The `%` sign must immediately follow a number. |
| **Percentage not at the start** | A percentage value cannot be the first entry in a calculation. |
| **Unknown function** | Function name not recognized. |
| **Invalid variable name** | Names must start with a letter and contain no special characters. |
| **Variable name already in use** | The name has been assigned more than once. |
| **Variable not defined / value undefined** | The variable used has not (yet) been defined. |
| **Variable definitions only in sum lines** | This definition form is only allowed in sum lines; otherwise put the name to the left of `=`. |

## 12. Limits & Notes

- **Maximum 500 lines** per calculation. From about 95 % a banner above the
  status bar shows how many lines are used; at 500 lines it turns red.
- **At the limit** only **new lines** are rejected (Enter, keys with an
  automatic line break) – the banner then shakes briefly. Typing within
  existing lines, deleting and undo keep working.
- **Paste from clipboard:** if the content no longer fits completely, a dialog
  asks whether to insert only the beginning that still fits – with a note that
  a truncated calculation may yield different results.
- **Longer calculations from earlier versions** are loaded in full and never
  truncated; they just cannot grow further. For more extensive calculations,
  the CalcTape apps are recommended.
- **Undo** only works as long as the tab is open and has not been reloaded.
  The undo history is also limited to a fixed amount of memory; with very
  large calculations the oldest steps are dropped first.
- **Internal error:** should the calculation engine unexpectedly stop (e.g.
  due to memory exhaustion), a dialog with a **Reload page** button appears.
  After reloading, the calculation is restored from the last automatic save
  (section 9).
- CalcTape Web uses **WebAssembly**; in very old browsers without WebAssembly
  support, a fallback version is used automatically.
- **On a phone or tablet:** The web app is made for the browser on a computer; on small screens it works only to a limited extent – the on-screen keyboard interferes with input, among other things. There, our CalcTape apps for iOS and Android, designed specifically for mobile, are the better choice.

## 13. Privacy

CalcTape Web stores your **settings and calculations exclusively locally** on
your device. This data is **never transmitted over the internet**, not even
when sharing via link (the content is embedded in the link itself, not on a
server).

The flip side of purely local storage: calculations are lost when **browser
data is cleared** or in **private/incognito mode**. A one-time notice on first
start points this out – save important calculations **as a file** or **share
them as a link** from time to time (Sections 8 and 9). No liability is
accepted for lost data.

The privacy policy, legal notice, and contact information are available via the
links in the **footer**.

## 14. CalcTape for Other Platforms

CalcTape is also available as a full-featured app with additional functionality
for:

- **Windows**
- **macOS**
- **Android**
- **iOS / iPhone**
- **CalcTape for Business (Enterprise)**

You can find the links in the **Apps panel** below the keyboard, in the menu,
and at [calctape.com](https://calctape.com/en/). Files saved from CalcTape Web
can be opened and edited in these apps as well.

*© schoettler Software GmbH – CalcTape Web. This manual describes the
user interface of the web version. Everything else about CalcTape can be found
at [calctape.com](https://calctape.com/en/).*