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# Truncation
- URL: https://www.esheets.io/truncation/
- Published: 2024-11-27T21:14:50.000Z
- Updated: 2026-06-21T16:47:18.000Z
- Author: Richard Linnington
- Tags: Maths, Number

Truncation is a way of simplifying numbers by cutting off extra decimal places or digits, often used in calculations to save time or achieve a specific level of accuracy. You might see truncation in action when rounding financial figures, measuring distances, or programming computers to work with manageable numbers. [Jump to the questions](#practise-now)

## Practise now

Worksheet preview and key skills 

### Worksheet preview

Practise truncation with this self-marking maths worksheet.

The interactive worksheet below generates questions, gives instant feedback, and lets students record their score.

#### What you’ll practise

- Cutting a number off at the required place value or decimal place.
- Distinguishing truncation from rounding.
- Keeping digits before the cut-off point unchanged.
- Writing the truncated value accurately.

Use the interactive worksheet below, or read the [Topic guide](#topic-guide) for the method and worked example.

## Topic guide

### What this worksheet practises

This worksheet focuses on "truncating" numbers. Truncation is a very blunt, aggressive form of rounding. Instead of looking at a "decider" digit to see if a number should round up, truncation simply chops off everything after a certain point and ignores it completely.

### Key method

Truncation does not care what the following digits are; it never rounds up.

- Identify the position you are asked to truncate to (e.g., 2 decimal places, or 1 significant figure).
- Find that exact digit in the number.
- Imagine a solid wall immediately after that digit.
- **Chop off and delete** every single digit that falls behind the wall. Do not look at them, do not use them to round up.
- If you are truncating a large whole number (e.g., to the nearest 1000), replace the chopped digits with placeholder zeroes to keep the number the right size.

### Worked example

**1) Truncate 14.899 to 1 decimal place.** 
**2) Truncate 5,682 to 1 significant figure.**

Example 1: (14.899 to 1 d.p.)

Step 1: The 1st decimal place is the 8\. Draw the wall after the 8: 14.8 | 99

Step 2: Chop off the 99 entirely. (Note: standard rounding would make this 14.9, but truncation does not care).

The answer is 14.8.

Example 2: (5,682 to 1 s.f.)

Step 1: The 1st significant figure is the 5\. Draw the wall after the 5: 5 | 682

Step 2: Chop off the 682\. We must use placeholder zeroes because 5,682 is in the thousands.

The answer is 5,000.

### Common mistakes to avoid

The most common mistake is simply forgetting that truncation is different from normal rounding. If a student is asked to truncate 7.96 to 1 d.p., habit will force them to round it up to 8.0\. You must fight this habit. Truncation means CHOP. The answer is 7.9.

### Things to remember

Truncation is often used in computers or digital displays when there is limited screen space. If a calculator screen can only show 5 digits, and the answer is 1.666666, it will simply truncate it to 1.6666, rather than doing the complicated arithmetic to round the final digit up to a 7.