How to read a z-table
- Round z to two decimal places, e.g. 1.96.
- Find the row for the first decimal (1.9) in the left column.
- Move across to the column for the second decimal (0.06).
- The cell (0.9750) is the area to the left of z, P(Z < 1.96).
For the area to the right, subtract from 1 (1 − 0.9750 = 0.0250). For the area between −z and z, subtract twice the right-tail area from 1 (0.95 here, which is where the 1.96 in 95% confidence intervals comes from).
Negative z-scores
The curve is symmetric, so P(Z < −z) = 1 − P(Z < z). The negative table saves you that subtraction: z = −1.25 is row −1.2, column 0.05, giving 0.1056. Values beyond ±3.49 are extremely close to 0 or 1; the z-score calculator handles any z exactly.
Frequently asked questions
What z-score gives 95%?
1.645 for 95% in one tail (area to the left = 0.95) and 1.960 for 95% in the middle (two-tailed).
Is this a left-tail (cumulative) table?
Yes. Every cell is the cumulative area from −∞ to z. Some textbooks use a “0 to z” table instead; subtract 0.5 from these values to convert.