Usage notes

Getting started

• Enter a value, optionally add a note, then confirm with ↵ or Enter. Use the pencil beside the calculation title to rename it.
• In the value field, +, −, × and ÷, or the keyboard characters +, -, * and /, select an operation. During normal entry, an existing number is first submitted using the previously selected operation. Further operators without a new number only change the selection.
• Use ± or paste a signed number to enter negative values. The keyboard minus key selects subtraction rather than typing a minus into an empty value field.
• A comma or point is accepted as the decimal separator; thousands separators are not supported. Enter 1234.50 or 1234,50, not 1,234.50.
• Typing digits outside an input field sends them to the value field; letters start a note. Active text fields and open dialogs retain their normal behaviour. The info button in the result display explains the selected operation.

Sequential calculator logic, not operator precedence

Steps run in sequence. Each active step uses the previous result. Therefore 100 + 20, followed by × 2, gives 240, not 140.

“Starting value / replace” replaces the running value. Subtotals and note-only steps do not change it. Disabled steps are skipped but remain in the calculation.

Editing the tape and choosing a view

• The default is the simplified receipt view with notes and calculation lines. Select a step to reveal its enable switch and actions; select it again to collapse them.
• Edit, insert before, reorder, disable or delete steps. All following results recalculate. Drag and drop is also available in the detailed view.
• Settings let you switch between simplified and detailed views and choose which side the calculator occupies when the panels are side by side. Focus view hides the surrounding page sections.
• Undo and redo apply to calculation changes, including new calculations, imports and examples. Up to 100 undo snapshots are kept. Input drafts and history are not saved with the calculation.

Percentages, gross and net

• Percentage increases and discounts use the previous result as their base. Starting from 200, a 10% increase gives 220 and a 10% discount gives 180.
• “Add tax / gross amount” adds the entered tax to the previous net amount: net × (1 + rate / 100). For example, 100 with an entered rate of 19 gives a gross amount of 119.
• “Remove included tax” returns the net amount: gross ÷ (1 + rate / 100). Thus 119 with an entered rate of 19 gives 100. The result is the net amount, not the tax removed.
• You enter the percentage yourself. The tool does not choose a tax rate applicable to your situation.

Decimal places and rounding

Internally, the tool uses exact fractions instead of binary floating-point numbers. By default, only the display is rounded to two decimal places. Settings allow zero to eight decimal places.

“Round every step” also rounds each intermediate result before the next step. This can change the final result: 1 ÷ 3 × 3 gives 1.00 with display-only rounding, but 0.99 when rounding each step to two decimal places.

Exact halfway values round away from zero: 1.005 becomes 1.01 and −1.005 becomes −1.01. Displayed and printed values can therefore show fewer digits than the stored input. Editing and JSON export retain the original input precision.

Currency as a label

Choose a currency or “No currency” under Settings → Currency. The choice belongs to the calculation and labels results, printouts, copied text and exports.

Selecting another currency does not convert amounts, retrieve exchange rates or change decimal places or rounding. The numbers stay unchanged. Do not mix amounts in different currencies within one calculation.

Local saving and backups

Without saving enabled, reloading, leaving the page or switching language can lose the calculation. “Save this calculation on this device” automatically saves the current calculation in this browser. Unsubmitted input drafts are not saved. Confirm important steps before navigating away.

Saving language and appearance is separate and optional. “Local settings” → Delete removes saved preferences and the saved calculation; the currently visible calculation initially stays open. There is no synchronisation or server backup.

Calculations run in your browser; the tool does not send calculation data to a server. Browser data can be deleted or be temporary in private browsing. Local saving is not a backup: download important calculations as JSON files as well.

Files, copying and Print / PDF

• JSON saves the editable calculation, including disabled steps, original input values, notes, currency and calculation settings. Open the file again later. After confirmation, a valid imported file replaces the current steps.
• CSV is intended for spreadsheets; Copy places the tape on the clipboard as text. Both include disabled steps with their status. CSV uses semicolons as separators. Potentially formula-like cells are protected with an apostrophe.
• Print / PDF includes active steps only, with step number, note, operation and result. Values use the selected decimal places. Currency and rounding settings also appear on the printout. Original step numbers are retained, so skipped steps can leave gaps.
• To save a PDF, select the PDF option in your browser’s print dialog, if available. You can then attach the saved file to an email yourself. The tool does not send calculations.

Example calculations

The book icon opens examples for a family budget, holiday planning and a tradesperson’s calculation. Values are illustrative, not statistical averages or complete invoices. All steps remain editable.

Loading an example replaces the existing calculation and input drafts after confirmation. Examples use two decimal places with rounding at each step. Check the settings afterwards and choose a currency if needed.

Errors and limits

A calculation supports up to 500 steps, with up to 24 integer digits and 12 fractional digits per input. Additional technical safeguards apply to very large intermediate values.

Division by zero or exceeded calculation limits are shown on the affected step. Following results remain invalid until you correct, delete or disable the first problematic step. A new starting value after the error does not bypass it.

The tool is free and requires no account; support is optional. Independently verify important results and the rounding rules your purpose requires. This tool does not replace accounting software or professional advice.