Use configurable digit weights.
Initialising algorithm engine for Weighted Modulus 10 Calculator...
How Weighted Modulus 10 Calculator Works?
The Weighted Modulus 10 Calculator works by multiplying each digit by a user-defined repeating weight, summing the products, and taking the difference between the sum's last digit and 10. The default weight cycle is 7-3-1 applied from the left.
- 1Enter the payload digits and the weight cycle (for example 7, 3, 1 or 3, 7, 1).
- 2Choose the direction: weights start from the leftmost or the rightmost digit.
- 3Repeat the weight cycle until every digit has a weight.
- 4Multiply each digit by its weight and add the products.
- 5Subtract the last digit of the weighted sum from 10 to get the check digit (0 stays 0).
Weighted Modulus 10 Calculator Formula
The Weighted Modulus 10 formula is Check Digit = (10 − (Σ dᵢ·w₍ᵢ mod k₎ mod 10)) mod 10, where k is the length of the weight cycle.
S = Σ dᵢ × w[(i − 1) mod k] Check Digit = (10 − (S mod 10)) mod 10 (WEIGHTED MODULUS 10)
wis the weight cycle of length k.dᵢis digit i in the chosen direction.Sis the weighted sum.
1 × 7 = 7 2 × 3 = 6 3 × 1 = 3 4 × 7 = 28 5 × 3 = 15 6 × 1 = 6 7 × 7 = 49 8 × 3 = 24 9 × 1 = 9 0 × 7 = 0 S = 147 Check digit = (10 − (147 mod 10)) mod 10 = 3
Weighted Modulus 10 Calculator Conversion Table
The Weighted Modulus 10 conversion table compares common weight cycles applied to the same payload 1234567890.
| Weight cycle | Direction | Used by | Weighted sum | Check digit |
|---|---|---|---|---|
| 7 - 3 - 1 | Left | Finnish reference style | 147 | 3 |
| 3 - 7 - 1 | Left | ABA routing numbers | 159 | 1 |
| 3 - 1 | Right | GS1 keys | 85 | 5 |
| 1 - 3 | Right | Reverse GS1 variant | 95 | 5 |
| 2 - 1 | Left | Unfolded Luhn variant | 70 | 0 |
| 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 | Left | Linear weights | 285 | 5 |
| 9 - 7 - 3 - 1 | Left | Four-weight cycle | 233 | 7 |
The Unfolded Luhn variant multiplies without subtracting 9, so its result differs from a true Luhn digit.
What is Weighted Modulus 10 Calculator?
A Weighted Modulus 10 Calculator is a configurable tool that computes a decimal check digit from any repeating weight pattern. The tool covers schemes such as American Bankers Association (ABA) routing numbers, Finnish payment references, and in-house serial numbers.
The weight cycle decides the error coverage. Weights that share no factor with 10 (1, 3, 7, 9) catch every single-digit error, while even weights such as 2 or 4 miss 1 in 9 substitutions.
What are the uses of Weighted Modulus 10 Calculator?
There are 4 main uses of the Weighted Modulus 10 Calculator, including routing number checks, reference numbers, and scheme prototyping.
- Routing number checks: Banks and payroll teams test 3-7-1 weighted routing numbers.
- Payment references: Billers generate 7-3-1 weighted invoice references.
- Scheme prototyping: Engineers test weight cycles before fixing a new identifier format.
- Legacy system audits: Auditors reverse-engineer undocumented check digits in old databases.