How to Calculate Sum of Digits
What is Sum of Digits?
A digit sum calculator adds together all the individual digits of a number. The sum of digits of 12345 is 1+2+3+4+5 = 15. Digit sums are used in divisibility rules (a number is divisible by 9 if its digit sum is divisible by 9), check digit algorithms, and computing digital roots.
Formula
sum = d1 + d2 + d3 + ... + dn
Step-by-Step Guide
- 1Separate the number into individual digits
- 2Add all digits together
- 3The result is the digit sum
Worked Examples
Input
12345
Result
15
Used in divisibility rules and digital roots
Common Mistakes to Avoid
- ✕Including the decimal point in multi-digit sums
- ✕Forgetting negative signs don't affect digit sums
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