Z-Table (Standard Normal Distribution) Calculator and Z-Score Guide
Use the Z-Table Calculator below to quickly find probabilities, percentiles, critical Z-values, and confidence levels from the standard normal distribution. Enter a Z-score or select the calculation type to instantly visualize the corresponding area under the normal distribution curve.
The calculator also serves as a practical Z-table reference, helping students, researchers, engineers, quality professionals, and Six Sigma practitioners quickly perform probability calculations without manually searching standard normal distribution tables.
Z-Table Calculator with Normal Distribution Curve
Standard Normal Distribution
The shaded area represents the selected normal probability.
One Z-Score Probability
Results
What this result means
View Step-by-Step Solution
What Is a Z-Score?
A Z-score measures how many standard deviations a value is above or below the mean.
- x = observed or raw value
- mu = population mean
- sigma = population standard deviation
Common Critical Z-Values
Two-sided critical values for common confidence levels.
| Confidence | Two-sided critical Z |
|---|---|
| 80% | +/-1.282 |
| 90% | +/-1.645 |
| 95% | +/-1.960 |
| 98% | +/-2.326 |
| 99% | +/-2.576 |
| 99.9% | +/-3.291 |
Cumulative Z-Table
This table shows cumulative area to the left of a positive Z-score.
Explore Learning Topics
Choose a category below to explore practical tutorials, tools, calculators, templates, case studies, and learning resources.
Accelerate your learning with carefully selected courses, books, templates, and practical tools.
Expert-led courses to build skills and advance careers.
Explore CoursesRecommended books and professional study guides.
Explore BooksReady-to-use templates, guides, workbooks, and checklists.
Browse TemplatesPractical calculators for analysis and data-driven decisions.
Open Calculators
Published: August 27, 2026
Last Updated: September 16, 2026
