About Z Score Tables

Z Score Tables exists for one job: to be the most accurate, fastest and clearest z score table on the web — the page a student can trust at midnight before an exam, and a teacher can put in a course pack without checking it first.

How the values are made (and checked)

Every probability on this site — in the interactive tables, the PDF, the CSV and the downloadable images — is computed from the standard normal cumulative distribution function by a build script, from a single data source. Nothing is typed by hand and nothing is copied from another site's table, which matters more than it sounds: copied tables inherit each other's errors, and some widely used z table pages online today contain wrong values in their own worked examples. Ours cannot drift apart between formats, because all formats are rendered from the same computed dataset.

Before any build is published, the dataset is spot-checked against published reference tables at fixed anchor points: Φ(0.00) = 0.5000, Φ(1.00) = 0.8413, Φ(1.645) = 0.9500, Φ(1.96) = 0.9750, Φ(−1.96) = 0.0250 and Φ(2.576) = 0.9950. If an anchor fails, the build does not ship. Worked examples across the site are re-verified in a separate pass, because an example is where readers place their trust.

Who is behind the site

The site is built and maintained by the team at Harvest Click, a small web practice that builds focused educational tools and reference sites. Content is written to teaching standard — answer first, method shown, examples with real numbers — and reviewed against standard references for the topic, including open statistics textbooks (OpenIntro and LibreTexts) and NIST's published tables. We are not a university and do not pretend to be one; what we offer instead is verifiable accuracy, and an open invitation: if you find a wrong value anywhere on this site, email us and we will fix it and say what changed.

Using our tables

The tables, PDF, images and CSV are free for students, teachers and anyone else who needs them, including in classroom handouts and course packs — keep the source line on the file and link back where the format allows. The one thing we ask is that the files not be resold as a standalone product.

Contact

Corrections, requests and classroom feedback: hello@zscoretables.com, or the contact page. Corrections always jump the queue — accuracy is the whole reputation of a site like this, and we would rather hear about an error from you than have a thousand students copy it.