Standard Deviation Calculator
Calculate population and sample standard deviation and variance.
Your result
Updates as you type. Based on 2025/26 UK figures where relevant.
How this is worked out
Find the mean, square each value's distance from it, and average those squares (divide by n for population, n − 1 for a sample). The square root is the standard deviation.
Tips
- Write down which number is the 'whole' before working out any percentage.
- Round only at the end of a calculation, not in the middle.
- Check answers roughly in your head – does the result look sensible?
Guides for this calculator
- How to Calculate Standard Deviation in the UK: Step-by-Step Guide
- Standard Deviation: Common Mistakes, Tips and FAQs
More maths calculators
Frequently asked questions
How does the standard Deviation Calculator work?
Find the mean, square each value's distance from it, and average those squares (divide by n for population, n − 1 for a sample). The square root is the standard deviation.
Are these suitable for GCSE revision?
Yes. The methods match those taught in UK schools, and each page explains the formula used.
How many decimal places are shown?
Most results show up to two decimal places. Use the rounding in your working as your teacher or exam board requires.
Can I use negative numbers?
Yes, where they make sense mathematically, such as percentage change.
This calculator gives an estimate for general information. It isn't financial, tax, legal or medical advice. Check official figures on GOV.UK or NHS.uk, or speak to a qualified adviser.