In short: To round to a given decimal place, look at the next digit along: if it is 5 or more, round up; if it is 4 or less, round down. So 3.6471 to 2 decimal places is 3.65, because the next digit (7) rounds the 4 up to 5. The same rule works for rounding to significant figures.
Knowing how to round to a decimal place is a vital GCSE Foundation skill, used to tidy up answers, estimate sensibly and give money to the nearest penny. The same simple rule also lets you round to significant figures. This guide explains the rounding rule clearly, with worked examples for both decimal places and significant figures.
The reliable method
Rounding always comes down to one decision: do you round up or stay the same?
- Find the digit you are rounding to. For 2 decimal places, that is the second digit after the decimal point.
- Look at the next digit to the right. This is the deciding digit.
- Apply the rule. If the deciding digit is 5 or more, round the chosen digit up by 1. If it is 4 or less, leave the chosen digit as it is.
- Drop everything after the chosen digit. Once rounded, the remaining digits are removed.
- Keep any zeros that hold place value, especially when rounding to significant figures, so the number stays the right size.
For significant figures, the first significant figure is the first non-zero digit, counting from the left. Then the method is identical: find the place you want, look at the next digit, and round.
A worked example
Round 3.6471 to 2 decimal places, then round 4827 to 2 significant figures.
Rounding 3.6471 to 2 decimal places:
- The second decimal place is the 4 (in 3.64...).
- The next digit to the right is 7, which is 5 or more, so round up.
- The 4 becomes 5, and the rest is dropped.
- Answer: 3.65
Rounding 4827 to 2 significant figures:
- The first two significant figures are 4 and 8 (in 48...).
- The next digit to the right is 2, which is 4 or less, so round down (leave the 8).
- Replace the dropped digits with zeros to keep the size: 4800.
- Answer: 4800
This works because the deciding digit tells you which way the number is closer to. A 7 in the thousandths means 3.6471 is nearer to 3.65 than to 3.64, while a 2 means 4827 is nearer to 4800 than to 4900.
Common mistakes to avoid
- Trap: looking at the wrong deciding digit. Checking two digits along instead of the very next one. Fix: only the single digit immediately to the right decides the rounding.
- Trap: dropping place-holding zeros. Writing 4827 to 2 significant figures as 48 instead of 4800. Fix: keep zeros so the rounded number stays roughly the same size.
- Trap: rounding up every digit in a chain. Changing 3.6471 to 3.66 by rounding more than once. Fix: round in one step using the original deciding digit, not repeatedly.
- Trap: muddling the place value columns. Counting decimal places from the wrong side. Fix: see [decimal place value explained](/misconceptions/decimal-place-value) to keep tenths, hundredths and thousandths clear.
Frequently asked questions
How do you round a number to 2 decimal places? Look at the third digit after the decimal point. If it is 5 or more, round the second decimal digit up by 1; if it is 4 or less, leave it. Then drop the rest. For example, 3.6471 rounds to 3.65 because the third digit is 7.
What is the rule for rounding up or down? If the deciding digit is 5 or more, round up. If it is 4 or less, round down (leave the digit as it is). The deciding digit is always the one immediately to the right of the place you are rounding to.
How do you round to significant figures? Find the first significant figure (the first non-zero digit from the left) and count along to the place you want. Then look at the next digit and apply the same rounding rule. Keep zeros at the end to hold the place value, such as 4827 rounding to 4800.
What is 7.348 rounded to 2 decimal places? The third decimal digit is 8, which is 5 or more, so round the second decimal digit up. The 4 becomes a 5, giving 7.35.
What is the difference between decimal places and significant figures? Decimal places count digits after the decimal point. Significant figures count meaningful digits starting from the first non-zero one, anywhere in the number. So 0.0526 has two significant figures in 0.053, but that is 3 decimal places.
Practise this
Find out which mistakes cost marks — [take the free diagnostic](/diagnostic). Related: [decimal place value explained](/misconceptions/decimal-place-value).