Rounding Calculator
Decimal places, significant figures, or a nearest multiple.
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Rounding replaces a number with a simpler nearby value. Choose how you want to round — to a number of decimal places, to significant figures, or to the nearest 10/100/1000 — and the calculator shows the result, plus the round-up and round-down values for decimal mode.
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How to Round a Number — The Quick Answer
Look at the first digit you're dropping. If it's 5 or more, round the kept digit up; if it's 4 or less, leave it. That's the standard 'round half up' rule used here, and it applies the same way to decimal places, significant figures, and nearest multiples.
Shortcut
digit being dropped ≥ 5 → round up | ≤ 4 → round down (keep as is)
The same number, rounded different ways
| Number | Rounded to | Result |
|---|---|---|
| 3.14159 | 2 decimal places | 3.14 |
| 3.14159 | 3 significant figures | 3.14 |
| 1,234 | nearest 100 | 1,200 |
| 1,250 | nearest 100 | 1,300 |
| 0.004567 | 2 significant figures | 0.0046 |
Decimal places count digits after the point; significant figures count meaningful digits from the first non-zero one. They often differ — 0.004567 to 2 decimal places is 0.00, but to 2 significant figures is 0.0046.
How It Works
The Rules
Three ways to round, one underlying rule
Formula
Look at the first dropped digit: ≥ 5 → increase the last kept digit by 1 ≤ 4 → leave the last kept digit unchanged
Variables
Digits after the point
Keep a fixed number of digits to the right of the decimal point. 3.14159 to 2 decimal places looks at the third decimal (1) — less than 5 — so it stays 3.14.
Meaningful digits
Count from the first non-zero digit. 0.004567 to 2 significant figures keeps the 4 and 5, looks at the next digit (6 ≥ 5), and rounds up to 0.0046. Leading zeros never count as significant.
Round to 10, 100, …
Divide by the multiple, round to the nearest whole number, then multiply back. 1,234 to the nearest 100 is 1,200; 1,250 rounds up to 1,300.
Note: This tool uses 'round half up' — a halfway digit (exactly 5 with nothing after) rounds up. Some fields use 'round half to even' (banker's rounding) to avoid bias over many values; the everyday-maths convention is half up.
Worked Example
Rounding 3.14159 and 1,234
3.14159 to 2 decimal places
Keep two decimals (3.14) and look at the next digit, 1. Since 1 < 5, leave it: 3.14.
3.14159 to 3 significant figures
The first three significant digits are 3, 1, 4. The next digit is 1 (< 5), so the result is 3.14.
1,234 to the nearest 100
1234 ÷ 100 = 12.34, which rounds to 12, then × 100 = 1,200.
Reference Guide
| unit | value | note |
|---|---|---|
| 3.14159 → 2 dp | 3.14 | decimal places |
| 3.14159 → 3 sf | 3.14 | significant figures |
| 1,234 → nearest 100 | 1,200 | nearest multiple |
| 1,250 → nearest 100 | 1,300 | half rounds up |
Key Features
Last updated: October 5, 2026
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Frequently Asked Questions
How do you round to a certain number of decimal places?
Keep that many digits after the decimal point and look at the next digit. If it's 5 or more, increase the last kept digit by one; if it's 4 or less, leave it. So 3.14159 to 2 decimal places is 3.14, because the third decimal (1) is less than 5.
What is the difference between decimal places and significant figures?
Decimal places count digits after the point regardless of value. Significant figures count meaningful digits starting from the first non-zero one. They often give different answers for small numbers: 0.004567 is 0.00 to 2 decimal places but 0.0046 to 2 significant figures.
How do I round to the nearest 10 or 100?
Divide the number by the multiple, round to the nearest whole number, then multiply back. For 1,234 to the nearest 100: 1234 ÷ 100 = 12.34 → 12 → × 100 = 1,200. A number ending exactly halfway, like 1,250, rounds up to 1,300.
What is 'round half up' versus 'banker's rounding'?
'Round half up' sends an exact halfway value (like 2.5) up to 3 — the rule taught in school and used by this calculator. 'Round half to even' (banker's rounding) sends halves to the nearest even digit (2.5 → 2, 3.5 → 4) to avoid a slight upward bias when rounding many numbers, and is common in finance and statistics software.