Basic Calculator

This calculator performs one operation at a time with a familiar keypad. It supports addition, subtraction, multiplication, division, sign change, square root, square, reciprocal, and percent conversion. A page-session history stores up to 20 displayed operations and can place a previous displayed result back on the keypad.

It is a sequential calculator, not an algebraic expression parser. It does not accept parentheses, variables, functions, or a pasted formula.

Operations used

For two displayed values a and b, the operator buttons apply a + b, a − b, a × b, or a ÷ b. Division by zero is rejected.

Unary buttons act on the current display:

• √ returns the non-negative square root and rejects a negative input;
• x² multiplies the current value by itself;
• 1/x returns the reciprocal and rejects zero;
• % divides the current value by 100;
• ± changes the sign.

The percent button does not automatically calculate “b percent of a previous value.” Entering 25 and pressing % produces 0.25; you can then use that number in the next operation.

Worked example

To calculate 12.5 × 8:

1. enter 12.5;
2. press ×;
3. enter 8;
4. press =.

The calculator displays 100 and adds 12.5 × 8 = 100 to the in-page history.

Operation order follows the buttons pressed. If you press 2 + 3 × 4 =, the calculator first completes 2 + 3, then multiplies that result by 4, so it displays 20. It does not apply the algebraic multiplication-before-addition rule that would produce 14.

For the percent button, entering 25 and pressing % displays 0.25.

How to interpret the result

The display formats ordinary values for readability and may use exponential notation for very large or very small results. Commas shown in history are display separators, not part of the stored arithmetic value.

C clears the current calculation state. CE resets only the current entry. The dedicated Clear History button removes the page-session history; clearing the calculation does not remove that list.

Keyboard digits, +, -, *, /, decimal point, Enter or =, Backspace, and Escape map to their visible keypad actions while the calculator has focus.

Accuracy and limitations

Calculations use the ECMAScript Number type, which represents IEEE 754 double-precision binary floating-point values. Many decimal fractions cannot be represented exactly in binary, so results such as 0.1 + 0.2 may contain a tiny internal rounding difference even when the display rounds it for readability.

The display is not an arbitrary-precision decimal, financial, statistical, or scientific calculator. Repeated operations can accumulate rounding. Integers beyond JavaScript's safe-integer range and measurements requiring controlled significant figures need a suitable decimal, integer, or specialist tool.

History is kept only in the current page instance and is not an audit record. Recheck consequential tax, accounting, engineering, laboratory, medication, and contractual calculations with the rules and precision required for that task.

Sources

• ECMAScript Language Specification — The Number Type
• IEEE — IEEE 754 Standard for Floating-Point Arithmetic
• ECMAScript Language Specification — Arithmetic operators

Editorial record

Written and manually reviewed by the SoupCalc Editorial Team. Binary, unary, sequential-operation, error, and percent behavior were checked against the current implementation and automated tests. Last reviewed: August 10, 2026. This page remains unavailable for indexing and advertising until all approved localizations pass review.