Basic Arithmetic Calculator

How to Use This Calculator

Choose the mode that fits your intent. The Two numbers tab lets you supply two separate values and pick an operation, while the Expression tab evaluates any valid arithmetic expression with standard order of operations.

• Enter values or an expression, then click the Calculate button to refresh the result.
• Reset buttons return the form to the original defaults and rerun the calculation.
• Use the swap control to swap the two-number inputs without retyping.
• Expression mode accepts parentheses, decimals, and negative signs so you can mimic textbook steps.

Methodology

The calculator operates on fundamental arithmetic rules. Two-number mode performs one operation between the chosen values, while expression mode applies the standard PEMDAS/BODMAS ordering.

• Addition ( + ) combines quantities into one total.
• Subtraction ( − ) finds the difference by moving from the first value toward or away from the second.
• Multiplication ( × ) scales one value by another, equivalent to repeated addition with sign rules.
• Division ( ÷ ) splits a value into equal parts; dividing by zero is undefined and is blocked by validation.

Order of operations (PEMDAS / BODMAS)

Expressions are evaluated in the default sequence: parentheses, exponents, multiplication/division (left-to-right), and addition/subtraction (left-to-right). This page's expression evaluator mirrors that rule so everyone calculates the same result.

• P – Parentheses first.
• E – Exponents (powers and roots).
• M/D – Multiplication and division, from left to right.
• A/S – Addition and subtraction, from left to right.

For example: \(7 + 3 \times 2 = 7 + (3 \times 2) = 7 + 6 = 13\), not 20.

Working with negatives and decimals

Negative numbers represent values below zero and decimals represent fractions of a unit. The calculator accepts inputs like \(-3.5\), \(0.25\), or \(12.75\) and applies the sign rules you expect.

• \((-3) + 5 = 2\)
• \((-3) - 5 = -8\)
• \((-3) \times 5 = -15\)
• \((-15) \div 5 = -3\)

Use the calculator to verify classroom work or to double-check quick mental math. Expression mode is especially handy for showing you each operator's precedence.

Full original guide (expanded)