How to Calculate Standard Deviation in Excel?
Standard deviation shows how spread out numbers are from the average. Excel calculates it with built-in functions. This guide explains how to calculate standard deviation in excel in plain language, with formula steps, examples, a quick reference table, and common mistakes to avoid.
Last updated: June 2026.
Quick answer
Formula: Use =STDEV.S(range) for a sample and =STDEV.P(range) when your data is the full population.
Example: If your values are in cells A2:A11, enter =STDEV.S(A2:A11) for sample standard deviation.
How to calculate it step by step
- Step 1: Put numeric values in one column or row.
- Step 2: Decide whether the data is a sample or full population.
- Step 3: Use STDEV.S for sample data.
- Step 4: Use STDEV.P for population data.
- Step 5: Check blanks, text, and outliers before trusting the result.
For a quick hand-check of variance or square roots, the Scientific Calculator can support the Excel result.
Example table
| Situation | Calculation or meaning | Use case |
|---|---|---|
| STDEV.S | Sample standard deviation | Survey sample |
| STDEV.P | Population standard deviation | All values included |
| AVERAGE | Mean value | Useful companion formula |
Common mistakes
- Mixing units, such as inches with feet, percentages with decimals, or sample data with population data.
- Skipping the formula and copying a result without checking whether the inputs match the question.
- Rounding too early, which can change the final answer when several steps are involved.
- Using an estimate for a decision that needs an official source, professional review, lab instruction, medical advice, or accounting records.
When to use a calculator
A calculator is most useful when the formula is clear but the arithmetic could distract you. Use it to check multiplication, division, powers, square roots, percentages, fractions, and repeated scenarios. For learning, write the formula first, then use the calculator to confirm the final number.
Search variations this answers
People search this topic in different ways, including STDEV.S Excel, STDEV.P Excel, standard deviation formula Excel. Instead of creating separate thin pages for each variation, this article groups the shared intent into one complete explanation.