Math Tools
Online Calculator for Basic Arithmetic
Calculate basic arithmetic step by step with up to 12 displayed decimal places, keyboard controls, and temporary tab-only history without server storage.
Exact decimal fractions
Calculate basic arithmetic
Immediate left-to-right execution; history remains only in this tab.
Keypad
Basic calculator
Keyboard: 0–9, ., +, −, ×, ÷, Enter, Backspace, Delete = CE, Escape = C
Ready. Operations execute from left to right.
Temporary session
Calculation history
Select a result to reuse it. Nothing is stored after refresh.
No calculations yet. Press equals to add one.
Up to 12 displayed decimal places, half-up rounded. Not certified for regulated or significant-figure work.
Quick answer
How does this online calculator work?
The calculator supports addition, subtraction, multiplication, and division using immediate left-to-right execution as each operator is pressed; it does not parse a long expression with precedence. Decimal inputs become exact BigInt fractions before display is half-up rounded to at most 12 places.
How to use this tool
- Enter a number with the keypad or keyboard, then choose +, −, ×, or ÷.
- Press equals or Enter to add the result to temporary history; select a history item to reuse its result.
- Use CE for the current entry, C for the active calculation, Backspace for the last digit, and export the session history if needed.
How the calculation works
A decimal with at most 18 integer digits and 12 fractional places is parsed as a BigInt fraction and reduced by the greatest common divisor. Addition/subtraction use a common denominator, multiplication multiplies numerators and denominators, and division multiplies by the reciprocal while rejecting zero. Display output is half-up rounded to at most 12 places. Chained operators execute immediately from left to right like a basic calculator.
Examples
| Example | Input | Expected result |
|---|---|---|
| Decimal addition | |
0.3 |
| Displayed division rounding | |
0.333333333333 |
| Immediate left-to-right chain | |
20 because 2 + 3 executes before multiplication by 4 |
| Division by zero | |
An error is shown and no history row is added |
Limitations
- Only addition, subtraction, multiplication, division, and decimals are supported; there are no parentheses, powers, roots, scientific functions, or M+/M− memory.
- Operations execute immediately from left to right rather than using algebraic expression precedence.
- Input allows at most 18 integer digits and 12 fractional places; display is half-up rounded to at most 12 places and result size is bounded to protect responsiveness.
- Division by zero is rejected and errors are not added to history.
- Results are not certified accounting, financial, engineering, scientific, or legal evidence.
Frequently asked questions
Why does 2 + 3 × 4 return 20 instead of 14?
This is an immediate-execution basic calculator. It processes each operator from left to right rather than parsing a complete expression with algebraic precedence. Use an expression calculator with parentheses and precedence when you need 14.
How do C, CE, and Backspace differ?
C clears the active calculation state without deleting history, CE clears only the current entry, and Backspace removes the last digit of the current entry.
How precise are decimal results?
Decimal inputs are calculated as BigInt fractions rather than direct binary floating-point sums, but the screen displays at most 12 half-up-rounded places. It is not intended for domain-specific significant-figure or rounding policies.
Does the website store my numbers or history?
No. History exists only in memory for the current tab. It is not placed in a database, localStorage, or URL and disappears on refresh or close.
References
- ECMAScript specification — BigInt objects Verified 2026-07-31
- Legacy THcount — calculator Verified 2026-07-31
Content and calculation method last reviewed: