Use the formula: z = (x – μ) / σ
Identify x, the value you want to convert
Identify μ, the mean of the population or dataset
Identify σ, the standard deviation
Subtract the mean from the value
Divide the result by the standard deviation
If using a sample mean and sample standard deviation, use z = (x – x̄) / s
Check that the standard deviation is not zero
Interpret positive z as above the mean
Interpret negative z as below the mean