Cross Sum / Digit Root Calculator
Calculate the cross sum (sum of all digits) and the digit root (repeated digit sum until a single digit) of any number.
What Does This Tool Do?
The cross sum of a number is simply the sum of all its digits — for example, the cross sum of 1234 is 1+2+3+4 = 10. The digit root continues this process until you get a single digit — 10 becomes 1+0 = 1. This tool shows all the steps.
Key Features
How to Use This Tool
- Enter one or more numbers (one per line).
- Click Convert to calculate the cross sum and digit root.
- View the step-by-step reduction.
How It Works
All digit characters in the number are summed. If the sum has more than one digit, the process repeats until a single digit remains (the digit root). All steps are displayed.
Common Use Cases
Frequently Asked Questions
What is the digit root used for?
The digit root has a useful property: a number is divisible by 9 if and only if its digit root is 9. It's also used in numerology and as a simple error-detection checksum.
Is the cross sum the same as the digit root?
Not always — the cross sum is the first sum of digits. The digit root is the final single-digit result after repeatedly applying the cross sum.
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