Rounding Calculator
Round any number to a chosen number of decimal places or to the nearest 10, 100 or 1,000.
How it works
rounded = round(value × 10ᵈ) ÷ 10ᵈ
Shift the decimal point to put the rounding position at the units digit, round to the nearest whole number, and shift back. Rounding to "nearest 10" is the same idea with a negative d — divide by 10, round, multiply by 10. The digit just past the rounding position decides: 0–4 rounds down, 5–9 rounds up.
Worked example
3.14159 to 2 decimal places: shift to 314.159, round to 314, shift back to 3.14. The next digit was a 1, so it rounded down, with a rounding error of about −0.00159.
Frequently asked questions
How are exact halves handled?
This calculator uses the schoolbook half-up rule: 2.5 rounds to 3. Note that for negatives it rounds toward the larger value, so −2.5 rounds to −2. Banker’s rounding (half to even) is a different convention used in some accounting and statistics software.
Should I round in the middle of a multi-step calculation?
No — round only the final answer. Rounding intermediate values lets small errors pile up; carrying full precision until the end keeps the result honest.
Rounding vs truncating — what’s the difference?
Truncating just chops digits off (3.19 → 3.1); rounding moves to the nearest value (3.19 → 3.2). Truncation always biases toward zero, which is why rounding is the default almost everywhere.
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This calculator is for educational purposes. Double-check important results before acting on them.