What this calculator does
Deciles divide a sorted dataset into ten equal parts. D1 is the value below which 10% of the data falls, D5 is the median, and D9 is the value below which 90% of the data falls. This calculator computes any decile from D1 to D9 for the values you enter, and lists all nine deciles for reference.
How the calculation works
The calculator sorts your values, then uses linear interpolation between the two nearest ranked values to find the position of each decile, the same method used by common spreadsheet PERCENTILE.INC functions. For decile k, it locates the position k/10 of the way through the sorted list (counting from the first value) and interpolates if that position falls between two data points.
Enter at least 2 values for a meaningful result; more values give more reliable decile estimates. This tool is for general and educational statistical use.