Digit Sum Calculator
Enter a base-10 integer to add its digits in your browser with BigInt arithmetic.
A QUICK WALKTHROUGH
How to use this tool
- Enter a decimal integer with an optional leading minus sign.
- Leading zeroes are accepted and do not change the digit sum.
- Select Calculate to see the normalized integer and exact digit sum.
Decimal integers only
The input must contain only decimal digits, with one optional leading minus sign. Decimal points, plus signs, spaces, separators, and exponent notation are rejected.
Negative and leading-zero rules
A negative integer is evaluated by its absolute value. Leading zeroes are accepted, shown in the normalized value without redundant zeroes, and contribute zero to the sum.
Exact and bounded
BigInt arithmetic keeps the integer exact. Inputs are limited to 100,000 characters so very large values remain practical in a browser; the result is still exact within that limit.
GOOD TO KNOW
Common questions
Does a negative sign change the sum?
No. The calculator uses the absolute value, so -123 and 123 both have a digit sum of 6.
Are leading zeroes allowed?
Yes. They are accepted and contribute zero; the displayed normalized value removes redundant leading zeroes.
Can I enter decimals or scientific notation?
No. Only base-10 integers are accepted.
Is a large number rounded?
No. BigInt arithmetic preserves the exact integer and exact digit sum within the 100,000-character input limit.