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Z Score Calculator
Quick answer
If value is 85, mean is 70 and standard deviation is 10, the z score is 1.5.
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Z Score
1.5
How many standard deviations a value sits from the mean — 0 is exactly average, positive is above, negative is below.
You enter Value 85, Mean 70, Standard deviation 10. You get Z Score 1.5.
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See how the result changes
Each table re-runs this calculator with one value changed and everything else left as it is.
Z Score by value
If value goes from 85 to 128, z score changes from 1.5 to 5.8 (+287%).
| Value | Z Score |
|---|---|
| 42.5 | −2.75 |
| 63.8 | −0.62 |
| 85start | 1.5 |
| 128 | 5.8 |
| 170 | 10 |
Z Score by mean
If mean goes from 70 to 105, z score changes from 1.5 to −2 (−233%).
| Mean | Z Score |
|---|---|
| 35 | 5 |
| 52.5 | 3.25 |
| 70start | 1.5 |
| 105 | −2 |
| 140 | −5.5 |
Z Score by standard deviation
If standard deviation goes from 10 to 15, z score changes from 1.5 to 1 (−33%).
| Standard deviation | Z Score |
|---|---|
| 5 | 3 |
| 7.5 | 2 |
| 10start | 1.5 |
| 15 | 1 |
| 20 | 0.75 |
STATISTICS & PROBABILITY GUIDE
A quick guide to Z Score
Use it to get an accurate z score in seconds — free, with no sign-up.
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See your z score the moment you enter your numbers.
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The same standard formula runs on our server for every calculation.
How to Use the Z Score Calculator
1
Enter Value
Provide your value.
2
Enter Mean
Provide your mean.
3
Enter Standard deviation
Provide your standard deviation.
4
View Your Results
Get your z score instantly, calculated on our server.
What is Z Score?
This statistics & probability tool works out your z score instantly, so you don't have to do the math by hand.
“One quick calculation, so you always know your z score before you decide.”
What Affects Your Z Score
Your z score depends on the values below.
Value
Changing your value changes your z score.
Mean
Changing your mean changes your z score.
Standard deviation
Changing your standard deviation changes your z score.
Example Result
Here's what you can expect from a z score calculation:
- Value
- 85
- Mean
- 70
- Standard deviation
- 10
- Z Score
- 1.5
Frequently Asked Questions
- How does value affect z score?
- If value goes from 85 to 128, z score changes from 1.5 to 5.8 (+287%).
- How does mean affect z score?
- If mean goes from 70 to 105, z score changes from 1.5 to −2 (−233%).
- How to calculate z score?
- Fill in value, mean and standard deviation in the Z Score Calculator above and your z score is calculated instantly. Change any value to see how the result responds.
- What does an example z score calculation look like?
- If value is 85, mean is 70 and standard deviation is 10, the z score is 1.5.
- Is this calculator free to use?
- Yes — every calculator on this site is completely free, with no sign-up or account required.
- How accurate is this calculator?
- It uses the standard formula and calculates on our server for every request, so results are precise for the values you enter.
- Is my data saved anywhere?
- No. Nothing you enter is stored or sent anywhere unless you choose to share a link with your values included.
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