Rounding Calculator
Round to decimal places, significant figures, or the nearest 10, 100 or 1000 with clear explanations. Free rounding calculator for GCSE and IGCSE maths.
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Rounding Rules
Everything you need to learn rounding, broken down into simple, bite-sized cards.
1. What Does Rounding Mean?
Rounding makes numbers simpler and easier to work with. We round up or down depending on the digits in the number.
Look at the digit right after the place you're rounding to. If it's 5 or more, round up. If it's 4 or less, round down.
2. What Does Place Value Mean?
Place value is the value a digit has based on its position in a number. For example, in 456.78, the 7 is in the Tenths column so it's worth 0.7, while the 4 is in the Hundreds column so it's worth 400.
Knowing place value helps you round correctly. When a question says "round to the nearest tenth", you know to look at the Tenths column and check the digit after it.
3. What Are Significant Figures?
Significant figures (s.f.) are the important digits in a number, starting from the first non-zero digit. Zeros before it don't count. For example, in 0.00456, the significant figures are 4, 5, and 6.
Round 0.004562 to 3 s.f.:
- Skip the leading zeros (0.00...)
- The first three s.f. are 4, 5, 6
- Next digit is 2 (less than 5), so round down → 0.00456
4. How to Round to the Nearest 10 or 100?
To round to the nearest 10, look at the units digit. To round to the nearest 100, look at the tens digit. If that digit is 5 or more, round up. If it's 4 or less, round down.
5. How to Round to Decimal Places?
"Decimal places" (d.p.) means the number of digits after the decimal point. To round, find the digit in that place, look at the next one, and decide whether to round up or down.
6. How Do You Estimate in an Exam?
When a GCSE question says "estimate", round each number to 1 significant figure first, then do the calculation. Always show your rounded values.
Students often lose marks by not showing their rounded values. Always write 4.8 → 5, 19.2 → 20 and 0.53 → 0.5 before calculating.
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