How to Calculate Average (Mean): A Step-by-Step Guide
Finds the arithmetic mean of a list.
These calculations come up in school, at work and in daily life, from PSLE and O-Level practice to measuring a room for new flooring. Doing them by hand builds understanding, and a calculator lets you check the answer instantly.
What you need
- Numbers (separated by commas)
Step by step
- Enter the numbers (separated by commas).
- The results update as you type, or press Calculate.
- Read the mean first, then the supporting figures below it.
The formula
Mean = sum ÷ count.
Worked example
For example, with these inputs:
- Numbers (separated by commas): 12, 15, 9, 22, 15, 30
the calculator returns:
- Mean: 17.1667
- Sum: 103
- Count: 6
Practical tips
- Check your answer by working backwards from the result.
- When numbers are very large or small, scientific notation makes them easier to compare.
- Round only at the final step to avoid accumulated rounding errors.
- Use brackets to make the order of operations explicit.
Background
A quick mental estimate before calculating is a powerful check. If a room's floor area comes out at 4,000 square metres or a percentage comes out above 100% when it should not, you know to look again.
Rounding is a common source of small errors. Keep full precision during intermediate steps and round only the final answer to the number of decimal places or significant figures the question asks for.
These calculations appear throughout the Singapore syllabus, from primary school percentages and fractions to secondary school algebra and geometry. Understanding the formula makes problem sums easier because you can recognise which quantity is missing.
Related calculations
- Perimeter of a Rectangle Calculator: Calculates the perimeter of a rectangle from the measurements you enter.
- Perimeter of a Square Calculator: Calculates the perimeter of a square from the measurements you enter.
- Perimeter of a Triangle Calculator: Calculates the perimeter of a triangle from the measurements you enter.
- Perimeter of an Ellipse Calculator: Calculates the perimeter of an ellipse from the measurements you enter.
Want to skip the arithmetic? The free Average (Mean) Calculator does all of this instantly and updates as you type.
Run your own numbers: Average (Mean) Calculator