Z-Score Calculator
This z-score calculator helps you understand how far a value sits from the mean in standard-deviation units.
Enter the value, mean, and standard deviation to get a z-score and an approximate percentile.
It is especially useful in statistics classes, test analysis, and normal-distribution review.
The result is numeric and easy to compare across datasets.
Assumptions
- Percentile is estimated from the standard normal curve.
- This tool assumes the distribution is approximately normal.
- Standard deviation must be greater than zero.
How this calculator works
Formula used
The z-score formula is z = (x - mean) / standard deviation. The percentile is estimated from the standard normal distribution.
Example calculation
If a score is 85 with mean 70 and standard deviation 10, the z-score is 1.5 and the percentile is roughly 93rd.
Z-Score Calculator FAQ
Is this z-score calculator exact?
It is designed as a practical estimate or classroom calculator for z-score calculator. Results can differ if your teacher, textbook, software, or engineering workflow uses different assumptions, notation, or precision.
Who should use this z-score calculator?
Students, parents, teachers, and everyday users can use it for homework checks, class review, exam prep, and quick planning calculations on a desktop or phone.
Does this replace official coursework, lab software, or professional tools?
No. These pages are educational calculators for learning and general use. For graded work, lab reports, engineering decisions, or research, verify the result with your course method or professional software.