Z Score Calculator
Calculate z-scores and normal distribution probabilities from raw scores, mean and standard deviation, with percentile conversion
Calculator Interface
Interactive calculator will be available soon
Features
- ✓ One-click z-score from raw score, mean and standard deviation
- ✓ Convert z-scores to percentiles, probabilities and one/two-tailed intervals
- ✓ Built-in standard normal table — no lookup needed
- ✓ Batch data calculation with result export
- ✓ 100% local calculation — no uploads, ideal for students and researchers
How to Use
- Enter the raw score (X)
- Enter the population mean (μ) and standard deviation (σ)
- Choose the result type (z-score/percentile/probability)
- Click calculate to view the result and normal distribution explanation
FAQ
What is Z Score Calculator?
An online statistics tool. It calculates z-scores from raw scores, mean and standard deviation, and converts them to percentiles and normal distribution probabilities. Input: your raw score, mean and standard deviation. Output: z-score, percentile and probability results with one-click copy. Everything runs in your browser.
What is a z-score?
A z-score (standard score) measures how many standard deviations a data point is from the mean: Z=(X-μ)/σ. Z=0 means equal to the mean, Z>0 means above it, Z<0 means below it — enabling comparison across different distributions.
How do z-scores convert to percentiles?
A z-score corresponds to the cumulative probability under the standard normal curve; cumulative probability ×100% is the percentile. For example Z=1.96 ≈ 97.5th percentile, Z=0 = 50th percentile. The tool does this automatically.
What assumptions are required?
Z-score calculation assumes the data is normally distributed (or approximately so). You only need the raw score, population mean and standard deviation; you can also reverse-calculate a raw score from a known z-score.
What is the difference between one-tailed and two-tailed probabilities?
One-tailed probability computes the chance of a value above (or below) a threshold; two-tailed probability computes the chance of falling outside ±Z, commonly used as the p-value in hypothesis testing.
Can I save the calculation results?
Yes. Results can be copied with one click, and batch calculations can be exported as CSV for homework, papers or lab reports.