Math Solver Free

Rounding Calculator

Decimals, significant figures, nearest 10/100/1000, floor & ceiling.

3.14159 rounded
3.14

Look at digit 3 after the decimal: 3.14159 โ†’ 3.14

โ† Back to All Calculators

How Rounding Works

Rounding replaces a number with a simpler nearby value. You round when exact precision doesnโ€™t matter โ€” estimating a bill, reporting a measurement, or cleaning up a long decimal โ€” and the key skill is choosing how much precision to keep.

Decimal Places vs. Significant Figures

Decimal places count digits after the point: 3.14159 to 2 decimals is 3.14. Significant figures count meaningful digits from the first non-zero digit: 0.004567 to 3 sig figs is 0.00457. Scientists prefer sig figs because they reflect real measurement precision.

Common Rounding Modes

  • Half up: 2.5 โ†’ 3 (the school standard, used by this calculator).
  • Floor / ceiling: always down or always up โ€” used in pricing, pagination, and capacity planning.
  • Nearest 10/100/1000: for big-picture estimates โ€” 4,782 to the nearest hundred is 4,800.

Crunching the numbers before rounding? Try our four-function calculator or the scientific calculator.

Frequently Asked Questions

What are the basic rules of rounding?

Look at the first digit you are dropping: if it is 5 or more, round the last kept digit up; if it is 4 or less, leave it. So 3.146 to two decimals is 3.15, while 3.141 to two decimals is 3.14.

What are significant figures?

Significant figures count the meaningful digits of a number, starting from the first non-zero digit. 0.00450 has three significant figures (4, 5, 0). They tell you how precise a measurement really is.

What is the difference between floor and ceiling?

Floor always rounds down to the nearest integer (floor of 4.9 is 4, floor of โˆ’4.1 is โˆ’5), while ceiling always rounds up (ceiling of 4.1 is 5, ceiling of โˆ’4.9 is โˆ’4).

Is this rounding calculator free?

Yes โ€” every tool on Math Solver Free is free with no sign-up, and all calculations run in your browser.