Rounding Calculator
Round any number to decimal places, significant figures or the nearest multiple. See round half-up, floor and ceiling side by side with an explanation.
About the Rounding Calculator
This rounding calculator rounds any number three different ways: to a chosen number of decimal places, to significant figures, or to the nearest multiple (nearest 10, 100, 0.5 — any step you like). Alongside the standard half-up result, it shows what floor (always round down) and ceiling (always round up) would give at the same precision, plus a plain-English explanation of which digit decided the outcome.
Half-up rounding is the rule taught in school: look at the first digit being dropped — 5 or more rounds the previous digit up, 4 or less leaves it alone. So 2.567 to 2 decimal places becomes 2.57 (the dropped 7 rounds the 6 up), while 2.563 becomes 2.56. Significant-figure rounding keeps a fixed count of meaningful digits regardless of the decimal point: 0.004567 to 3 significant figures is 0.00457, and 45,678 becomes 45,700.
Students use it for homework and lab reports where answers must carry a set number of sig figs; accountants and shopkeepers round to the nearest rupee, 0.5 or 10; and programmers use it to sanity-check floating-point rounding in their code.
How to Use the Rounding Calculator
- 1Enter the number you want to round.
- 2Choose the mode: decimal places, significant figures, or nearest multiple.
- 3Set the precision (e.g. 2 decimals, 3 sig figs, or a multiple like 10).
- 4Read the rounded result and compare half-up, floor and ceiling.
Frequently Asked Questions
How do I round 2.567 to 2 decimal places?
Look at the third decimal digit, 7. Since 7 ≥ 5, round the second decimal up: 2.567 → 2.57. If the number had been 2.563, the dropped 3 is below 5, so it stays 2.56. The calculator writes out exactly this reasoning for your number.
What are significant figures and how do they differ from decimal places?
Decimal places count digits after the point; significant figures count meaningful digits from the first non-zero digit. 0.004567 to 2 decimal places is 0.00, which destroys the value — but to 3 significant figures it is 0.00457. Sig figs are the standard in science because they track measurement precision.
How do I round to the nearest 10, 100 or 0.5?
Divide by the multiple, round to the nearest whole number, multiply back. 847 to the nearest 10: 847 ÷ 10 = 84.7 → 85 → 850. Prices to the nearest 0.5: 23.68 ÷ 0.5 = 47.36 → 47 → 23.5. Choose 'nearest multiple' mode and enter any step.
What is the difference between rounding, floor and ceiling?
Rounding goes to the nearest value (ties go up in half-up mode); floor always goes down; ceiling always goes up. For 2.4: round 2, floor 2, ceil 3. For −2.4: round −2, floor −3, ceil −2. The comparison table shows all three so you can pick the rule your situation needs.
How are negative numbers rounded?
Half-up rounding works on the magnitude in most school conventions: −2.5 rounds to −3 (away from zero). Floor and ceiling behave differently: floor(−2.5) = −3 but ceil(−2.5) = −2. The calculator applies sign-aware half-up rounding and shows floor and ceiling alongside for clarity.