Basic Calculator —
add, subtract, multiply, divide.

How to use it

A calculator that works the way you think.

This is a standard four-function calculator implementing the same logic you'd find in a physical desktop calculator or your phone's built-in app. Every button, edge case, and behaviour follows established calculator conventions, so if you've used a calculator before, everything works exactly as you expect.

The four operations

• Addition (+): combines two numbers. Supports chaining: press 5, then +, then 3, then ×, then 2, then = to get (5+3)×2 = 16. The calculator evaluates left-to-right as you enter operations.
• Subtraction (−): finds the difference between two values. Entering a negative number: press a digit, then ± to negate it.
• Multiplication (×): repeated addition. Standard chain evaluation: 3 × 4 + 2 evaluates as (3×4)+2 = 14, not 3×(4+2). This calculator follows sequential evaluation (no mathematical precedence — use parentheses mentally or compute sub-expressions first).
• Division (÷): distributes a total across equal parts. Division by zero returns an error; press any key to clear and continue.

Special buttons

• AC / C: All Clear resets the entire calculator including stored values and the pending operator. The button shows C (clear entry) when you have a number in progress, and AC when the slate is clean. One tap on C clears the current entry; tapping again (when the display shows 0) clears everything.
• ± (plus/minus): toggles the sign of the current display value, turning a positive number negative or vice versa. Works at any point in the calculation.
• %: converts the current number to a percentage. Used standalone (25% → 0.25), or in context: 200 + 15% adds 15% of 200 (i.e. 30), giving 230. This matches how financial calculators handle percentage additions and discounts.
• ⌫ (backspace): deletes the last digit typed. Only works while entering a number, not after pressing an operator or equals.

Memory functions

The four memory buttons store and retrieve a single value in a persistent memory register. A small M badge appears in the display when memory contains a non-zero value.

• M+: adds the current display value to memory. If memory is empty, it simply stores the value.
• M−: subtracts the current display value from memory. Useful for accumulating a running total of deductions.
• MR: recalls (displays) the stored memory value so you can use it in a calculation.
• MC: clears (resets) the memory register to zero. Greyed out when memory is empty.

Example: calculating a total bill — enter 12.50, press M+; enter 8.75, press M+; enter 3.00, press M+; press MR to see the total 24.25.

Chaining and repeat equals

This calculator follows standard sequential evaluation, not algebraic precedence (BODMAS/PEMDAS). Each time you press an operator, the pending operation is evaluated immediately:

• 3 + 4 × 2 = (3 + 4) × 2 = 14 — not 3 + 8 = 11
• If you need precedence, compute inner expressions first

Pressing = repeatedly repeats the last operation with the same second operand, a classic calculator shortcut for quickly adding or multiplying by the same amount:

• 2 × 3 = = = → 6, 18, 54 (multiplies by 3 each time)
• 100 − 10 = = = → 90, 80, 70 (decrements by 10)

Keyboard shortcuts

How decimal precision works

Computers store numbers in binary floating-point, which causes some decimal fractions to be represented with tiny rounding errors. The famous example: 0.1 + 0.2 = 0.30000000000000004 in raw JavaScript. This calculator rounds all results to 12 significant figures before displaying, which eliminates these artifacts while preserving full precision for all numbers you'd encounter in everyday use (up to 999,999,999,999 with full accuracy).