CALCULATE WITH CONFIDENCE

Number Fundamentals & Precision

Digit Sum Calculator

Add every decimal digit in an integer's magnitude.

Exact arithmetic

Add the digits of an integer

Up to 2,000 digits
  1. 1EnterProvide the known values
  2. 2CalculateResults update automatically
  3. 3VerifyReview the details and units
Try an example

Digit sum

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Understand the subject

What is a digit sum?

A digit sum adds the written base-ten digits once, ignoring the number's sign.

Use it for digit checks, divisibility patterns, puzzles, and quick inspection of a large whole number.

The key rule

What stays true

See the idea

Visual explanation

Example

Apply it

123456 has digit sum 21.

A digit sum is not automatically a digital root; this calculator does not repeat the addition.

Quick guide

How to use this calculator

  1. Enter a signed integer.
  2. The sign is ignored because it is not a digit.
  3. Read the exact sum and digit count.

Calculation method

Add the base-ten symbols

The calculator visits every digit once and adds its integer value. It does not repeatedly reduce the answer to a digital root.

Worked example

Digit sum of 123456

Add the six written digits once.

1 + 2 + 3 + 4 + 5 + 6 = 21

Supported inputs

Precision and limits

Integer length

Use at most 2,000 digits.

Distinct from digital root

Only one sum pass is performed.