Work out stanine score instantly with clear inputs, formula shown and shareable results.
Stanines divide the normal distribution into nine bands with mean 5 and standard deviation 2, so stanine = 5 + 2z rounded. The 75th percentile is z = 0.674, giving an exact stanine of 6.35 which rounds to 6 - the band covering the next 12% above the middle 20%. The coarseness is deliberate, discouraging over-interpretation of small differences.
Stanine
stanine = round(5 + 2z), bounded to 1-9
Band widths
4, 7, 12, 17, 20, 17, 12, 7 and 4 percent of the population
The scale was designed for punched cards in the 1940s, needing a single digit. The coarseness usefully discourages reading meaning into trivial score gaps.
In z units yes, at half a standard deviation each, but in population terms they vary from 4% at the extremes to 20% in the middle.