Free basic calculator calculator
Perform standard four-function arithmetic with parentheses — enter any expression using +, −, ×, ÷ to see the result, updated live, as you type.
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2 + 3 * 4Evaluates arithmetic expressions using standard order of operations. Only digits, +, −, *, /, and parentheses are accepted.
Results are estimates. Consult a professional.
How the basic calculator works
A basic calculator performs the four arithmetic operations — addition, subtraction, multiplication, and division — together with percentage and sign-change functions. When an expression contains more than one operation, the result depends on the order in which operations are applied. Calculators and mathematical convention both follow PEMDAS (also called BODMAS or BEDMAS in some countries): Parentheses first, then Exponents, then Multiplication and Division left to right, then Addition and Subtraction left to right.
Worked example: applying PEMDAS correctly
Two expressions that look similar but give different results because of where the parentheses go. Getting the order of operations right is the most common source of arithmetic mistakes.
PEMDAS order of operations examples
These examples show how PEMDAS resolves common expressions step by step. Read left to right within each precedence level.
| Expression | Step-by-step | Result |
|---|---|---|
| 2 + 3 × 4 | multiply: 2 + 12 | 14 |
| (2 + 3) × 4 | parentheses: 5 × 4 | 20 |
| 10 ÷ 2 + 3 × 4 | div+mult: 5 + 12 | 17 |
| 2² + 3 | exponent: 4 + 3 | 7 |
| (2 + 3)² | parentheses: 5² = 25 | 25 |
| 8 ÷ 4 ÷ 2 | left to right: 2 ÷ 2 | 1 |
| 50% of 80 | 80 × 0.5 | 40 |
Source: NCTM standard order of operations. Division before or after multiplication at the same level is resolved left to right.
Tips for accurate arithmetic
Even a simple calculator can give the wrong answer if you enter the expression incorrectly. These habits keep your calculations accurate.
- Use parentheses liberally — when in doubt, add parentheses to make the order explicit; extra parentheses never change a correctly ordered expression.
- Enter percentage as decimal for multi-step calculations — 15% tax on $80 is easiest as 80 × 1.15 = $92, not 80 + (80 × 15 ÷ 100).
- Check sign carefully for negative numbers — entering −3² gives −9 on most basic calculators (negation after squaring); use (−3)² = 9 if you want the square of a negative.
- Re-read the problem before calculating — most arithmetic errors are in reading the question wrong, not in pressing the wrong buttons.
- Estimate before you compute — round each number to one significant figure and compute mentally first; this sanity check catches order-of-magnitude errors before they matter.
Accuracy and limitations
This calculator uses JavaScript's 64-bit floating-point arithmetic (IEEE 754), which is exact for most everyday calculations. However, certain decimal fractions cannot be represented exactly in binary — the classic example is 0.1 + 0.2 = 0.30000000000000004. Results are rounded to 10 significant figures for display, which eliminates this noise for typical use. Division by zero returns an error. For financial calculations requiring penny-exact results, round intermediate steps yourself or use integer arithmetic (cents rather than dollars).
Key terms
About this calculator
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