Normal Distribution Calculator (Probability)
Math ToolsProbability below, above or between values on a bell curve
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The tool runs inside your visitor's browser, nothing is uploaded, and a small "Powered by ToolCloak" line stays under it. The second line (script) is optional: it makes the frame fit the tool's height.
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History
All history →Normal Distribution Calculator (Probability) — at a glance
Work out probabilities on a bell curve.
How to use it — step by step
Mean, standard deviation and the value x (and an optional second value).
Enter your values
Fill in the fields. Default numbers are shown so you can see how it works.
Press Calculate Probability
The answer appears at once as large result cards.
Copy or share
Copy the result, or share a link that opens with your numbers filled in.
Pro tips
Small things that make the result better.
Quick facts
Frequently Asked Questions
What is the z-score?+
How many standard deviations x is from the mean.
How accurate is it?+
About six decimal places, which is enough for study and work use.
Is my data safe?+
Yes. Everything runs inside your own browser. Your text, files and images are never uploaded to any server.
Is this tool really free?+
Yes — completely free, no signup, no watermark and no usage limit.