A walkthrough, end to end.
- 1
Enter a number and pick the rounding mode (decimal places, significant figures, or nearest multiple).
- 2
The calculator returns the rounded value plus the absolute error.
- 3
Supports half-up (standard) and half-even (banker's) rounding modes.
Rounding modes
Half-up: 0.5 always rounds up (standard). Half-even (banker's): 0.5 rounds to the nearest even digit (reduces bias on large datasets). For decimal places: round to a specific power of 10. For significant figures: count from the first non-zero digit.
What you can do with this.
Round to 2 decimal places
3.14159 → 3.14 (mode: decimal places, n=2). Most common rounding for currency and everyday display.
Round to significant figures
0.00123456 to 3 sig figs → 0.00123. Significant figures count from the first non-zero digit, ignoring leading zeros.
Round to nearest 5 / 10 / 100
127 to nearest 5 = 125; to nearest 10 = 130; to nearest 100 = 100. Useful for estimation, pricing, and visual displays.
Banker's rounding (half-even)
2.5 → 2 (rounds to even); 3.5 → 4 (already even). Reduces bias compared to half-up. Used in IEEE 754 floating-point and financial accounting.
Round currency
Two decimal places for most currencies (USD, EUR, GBP). Some currencies use 0 (JPY) or 3 (KWD, OMR). Calculator supports any decimal precision.
Scientific reporting
Significant figures preserve precision honestly. Measurement of 0.00456 ± 0.00012 should report 0.0046 or 0.005 (2 or 1 sig figs based on uncertainty).
Estimating large numbers
Round national debt to the nearest billion. Round populations to nearest thousand. Round revenues to nearest million. Calculator's 'nearest multiple' mode handles all of these.
Rounding 2026 — what's current
Standard math; unchanged. Modern programming languages mostly use half-even (IEEE 754); Excel uses half-up by default. Match your context.
Frequently asked.
Half-up always rounds 0.5 up. Banker's rounds to the nearest even (reduces bias on large datasets). IEEE 754 default is banker's; most schools teach half-up.
Counted from the first non-zero digit. 0.00123 has 3 sig figs. 1230 has 3 (ambiguous trailing zero) or 4 with a decimal point. Context matters.
Yes. Rounding mode applies to absolute value, then sign restored. −2.5 with half-up rounds to −3 (away from zero) by some definitions or −2 (toward zero) by others. Calculator follows JavaScript Math.round (away from zero for negatives).
No. Calculations run entirely in your browser.