How this calculation works
Positive multiples of 9 have digital root 9. Only the input zero produces digital root 0.
THE FORMULA
For n > 0, root = 1 + ((n − 1) mod 9)A worked example
582 becomes 15, then 1 + 5 = 6.
Good to know
The digital root of zero is zero.
Reference: OpenStax Prealgebra (opens in a new tab) ↗
Read the result
Repeatedly sum the decimal digits until one digit remains.
The primary result is labeled “Digital root”. Keep the input definitions in view when comparing this result with another method.
Try a related calculation
The digital root of zero is zero.
For a related exercise, try the fraction calculator.
A few questions, answered
How can I check the default inputs by hand?
582 becomes 15, then 1 + 5 = 6.
Which rule does this calculator apply?
For n > 0, root = 1 + ((n − 1) mod 9)