Rounding Calculator
Round to decimal places, significant figures, or the nearest 10, 100, or 1,000.
True half-up rounding, with the rounding error and both neighbours shown.
Decimal Places vs Significant Figures Decimal places count digits after the decimal point. 3.14159 rounded to 2 decimal places = 3.14
Significant figures count all meaningful digits from the first non-zero digit. 3.14159 rounded to 3 significant figures = 3.14 0.00314159 rounded to 3 significant figures = 0.00314
Standard Rounding Rules (Half-Up) If the digit being dropped is less than 5, round down (truncate). If the digit being dropped is 5 or more, round up, away from zero. Example: 2.345 rounded to 2 decimal places = 2.35 Example: 2.344 rounded to 2 decimal places = 2.34 Example: −2.5 rounded to the nearest integer = −3
Why the browser gets this wrong, and what this page does about it
JavaScript’s own rounding disagrees with the rule above in two places, and most rounding calculators inherit both mistakes.
Math.round(-2.5) returns −2, because it always rounds a tie toward positive infinity rather than away from zero.
And (1.005).toFixed(2) returns “1.00”, because 1.005 is not exactly 1.005 in binary floating point: the nearest double is a hair below it, so nothing is actually sitting on the tie.
This calculator sidesteps both by shifting the decimal point through the number’s text form before rounding, so 1.005 gives 1.01 and −2.5 gives −3, exactly as the half-up rule says.
Banker’s Rounding (Half-Even) A variant used in finance and statistics to reduce cumulative bias. When the dropped digit is exactly 5 with nothing after it, round to the nearest even digit instead. 2.345 → 2.34 (4 is even) 2.355 → 2.36 (6 is even) Round a thousand prices half-up and you gain about half a cent per tie; half-even splits those ties evenly and the bias cancels. The result panel shows you both so you can see when they differ.
Rounding to Powers of 10 To round to the nearest 10: divide by 10, round to integer, multiply by 10. To round to the nearest 100: divide by 100, round, multiply by 100. Example: 1,234 rounded to nearest 100 = 1,200
Common Use Cases Decimal places: money (2 places), measurements, scientific data Significant figures: scientific notation, engineering tolerances Nearest 10/100/1000: population estimates, financial summaries, quick approximations
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.