About the Decile Calculator

Deciles split a dataset into ten equal-frequency groups. D1 (the 10th percentile) is the value below which 10% of observations fall; D9 (90th percentile) has 90% below it. The middle decile D5 is the median — the value splitting the data in half.

Interpolation Method

For datasets whose size is not a multiple of ten, the boundary falls between two observations. This calculator uses linear interpolation (Excel's PERCENTILE.INC): the position p × (n − 1) is split into integer and fractional parts, and the boundary is interpolated between the two surrounding values — standard for statistical software.