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Z-Score Calculator

Standardize a value using mean and standard deviation.

Tool inputs stay in your browser · optional AI search sends your query

Good to know: z = (x−μ)/σ. Standard deviation must be positive. This does not infer a percentile unless the distribution is known.

How to use it (step by step)

  1. 1Fill in the boxes: “Observed value”, “Mean”, “Standard deviation”. Example numbers are already there so you can see how it works; replace them with yours.
  2. 2The result updates instantly as you type (on a phone it is below the boxes).
  3. 3The bold line is the main answer. Tap Copy next to any value to copy it.

Words to know

Average (mean) / median
Average = add everything and divide by how many. Median = the middle value when sorted; it is not pulled by extreme values.
Standard deviation
How spread out numbers are. Small = numbers are close together; big = they vary a lot.
Percentage
A part out of 100. 25% of 200 = 50.

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