Rounding Calculator
Round a number to any number of decimal places or significant figures, to the nearest 10, 100 or 1,000, and up or down — every common convention side by side.
Rounding to decimal places keeps digits after the point; rounding to significant figures keeps digits counted from the first non-zero digit, which is what science and engineering use.
How the rounding calculator works
Rounding to decimal places keeps digits after the point; rounding to significant figures keeps digits counted from the first non-zero digit, which is what science and engineering use. Half-up rounds 2.5 to 3; "round half to even" (banker's rounding) gives 2, which avoids bias in long sums.
Formula: round(x, d) = round(x × 10ᵈ) / 10ᵈ
Worked examples
| Inputs | Rounded to the decimal places | Note |
|---|---|---|
| 1234.5678 to 2 dp / 3 sf | 1234.57 | 1234.57 / 1230 |
| 2.5 to 0 dp | 3 | half-up 3, half-to-even 2 |
| 0.004567 to 2 sf | 0 | 0.0046 |
FAQFrequently asked questions
What is the difference between decimal places and significant figures?
Decimal places count from the point; significant figures count from the first non-zero digit, so 0.004567 to 2 sf is 0.0046 but to 2 dp is 0.00.
Which way does 2.5 round?
Half-up gives 3 (most schools); half-to-even gives 2 (banks and many computers), which keeps long sums unbiased.
When should I use significant figures?
Measurements: a result cannot be more precize than the least precize input.
How do I round to the nearest thousand?
Look at the hundreds digit: 1,234.57 → 1,000; 1,634 → 2,000.
Why does my computer show 0.1 + 0.2 as 0.30000000000000004?
Binary floating point cannot store 0.1 exactly; rounding to a sensible number of places fixes the display.
Where these figures come from
- NIST Digital Library of Mathematical Functions — reference definitions for elementary and special functions
- Wolfram MathWorld — definitions and formulas for every topic on this page
- NIST/SEMATECH e-Handbook of Statistical Methods — the statistical formulas (mean, variance, z, confidence intervals, sample size)
- Common Core State Standards — Mathematics — the terms and methods taught in US schools
Last checked: September 2026. Formulas are fixed by mathematics and do not change with tax years or regulations.