What is rounding?
Rounding means changing a number to a simpler, nearby value, usually to make it easier to read, compare or use in money calculations.
Rounding means replacing an exact number with a nearby simpler number. You might round £12.486 to £12.49, 48.6% to 49%, or 1.6667 to 1.67.
Rounding is useful because exact numbers can be too long for everyday use. It is especially common in money, VAT, discounts, percentages, measurements and unit-price comparisons.
Why rounding matters
Rounding makes results easier to understand, but it can also change totals slightly. This matters when you are adding VAT, splitting a bill, comparing unit prices or showing a final price to two decimal places.
Basic rounding rule
The common rule is to look at the next digit after the place you want to round to.
- If the next digit is 0, 1, 2, 3 or 4, round down.
- If the next digit is 5, 6, 7, 8 or 9, round up.
12.486 rounded to 2 decimal places = 12.49In this example, the third decimal place is 6, so the second decimal place rounds up.
Rounding money
Money values are usually rounded to two decimal places because pounds and pence are written with two digits after the decimal point.
| Exact value | Rounded to money | Why |
|---|---|---|
| £19.994 | £19.99 | The third decimal is 4, so it rounds down. |
| £19.995 | £20.00 | The third decimal is 5, so it rounds up. |
| £12.486 | £12.49 | The third decimal is 6, so it rounds up. |
Rounding with VAT and discounts
VAT and discount calculations often create decimal results that need rounding. For example, adding 20% VAT to £16.66 gives £19.992 before rounding, which is normally shown as £19.99.
Need to round a VAT result?
Use the VAT calculator to add or remove VAT and show the net price, VAT amount and gross price clearly.
Discounts work the same way. If a percentage discount produces a long decimal, the final sale price is usually rounded to the nearest penny.
Decimal places and significant figures
Rounding to decimal places keeps a fixed number of digits after the decimal point. Rounding to significant figures keeps a chosen number of important digits, starting from the first non-zero digit.
| Number | Rounded type | Result |
|---|---|---|
| 3.14159 | 2 decimal places | 3.14 |
| 3.14159 | 3 decimal places | 3.142 |
| 0.004876 | 2 significant figures | 0.0049 |
Common rounding mistakes
- Rounding too early in a calculation, then using the rounded number for later steps.
- Mixing rounded percentages with exact money totals.
- Comparing unit prices rounded to different decimal places.
- Forgetting that £19.995 rounds to £20.00 when shown to the nearest penny.
As a general rule, keep full precision while calculating and round the final result for display.
Rounding FAQs
What does rounding mean?
Rounding means changing a number to a nearby simpler value, such as changing 12.486 to 12.49 when showing money to two decimal places.
Do you round 5 up or down?
In the common everyday rule, 5 rounds up. For example, 2.345 rounded to two decimal places becomes 2.35.
Why do calculators sometimes show slightly different totals?
Small differences can happen when one calculator rounds each line separately and another keeps full precision until the final total.
How many decimal places should money use?
UK money values are normally shown to two decimal places because pounds and pence are written with two digits after the decimal point.