Digital Root Calculator
Repeatedly add the decimal digits of a nonnegative integer until one digit remains.
Formula
dr(0)=0; dr(n)=1+((n−1) mod 9) for n>0.
Digital root ≈ (987)-9×floor(((987)-1)÷9)
How to use
- Enter a nonnegative whole number.
- Use at most 1,000,000,000,000.
- Read the final single digit.
Examples
- 987 → 24 → 6.
Frequently asked questions
Is this a single digit sum?
No. Add digits repeatedly until only one digit remains.
What happens for multiples of nine?
Positive multiples give 9; zero gives 0.
Are decimals supported?
No. This definition uses nonnegative base-10 integers.
Sources
Updated: