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Tools / Modulo 11 Check Digit Calculator
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Modulo 11 Check Digit Calculator

Calculate or validate an ISBN-10 check character using the documented Modulo 11 weighting method. Enter your known values; results update as you type.

Inputs

Enter digits without spaces or hyphens. A complete ISBN-10 may end in uppercase X.

Calculated result

Check character2
Complete ISBN-100306406152
0×10 + 3×9 + 0×8 + 6×7 + 4×6 + 0×5 + 6×4 + 1×3 + 5×2 = 130 Check value = (11 − (130 mod 11)) mod 11 = 2
This page implements the ISBN-10 weighting method only. Modulo 11 has other industry-specific variants and is not the GS1 check-digit algorithm.

How to use this calculator

Start with the deterministic fixture values already shown, then replace each input with measurements from your job. Use consistent units and review the highlighted assumptions before using the result in purchasing or production.

Formula and method

This implementation multiplies the nine ISBN body digits by weights 10 through 2. The check value makes the complete weighted sum divisible by 11; value 10 is represented by X.

Read the methodology and source notes →

Worked example

For ISBN body 030640615, the weighted sum is 130. The check character is 2, producing ISBN-10 0306406152.

How to interpret the result

Use this page only for the legacy ISBN-10 weighting method. The explicit variant prevents a result from being mistaken for another industry's Modulo 11 rule.

Limitations

Modulo 11 is a family of schemes with different weights and remainder mappings. This calculator is not a generic Modulo 11 implementation and is not a GS1 calculator.

Optional partner module · disabledCategory placeholder: measuring tools. No products, reviews, prices or outbound links are configured.

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