Check Digit Calculator
Calculate or verify a check digit for a barcode, card number, IMEI, container code or security identifier. Follow each step of the calculation.
Check digit calculator and validator
EAN-13 / GTIN-13
Retail & BarcodeInternational retail barcode format used globally on supermarket and consumer goods.
Ready for packaging & scanner reading
Valid Check Digit
The provided check digit matches the expected calculation.
Real-Time Barcode & Symbology Preview
Live SVG RenderingVisualizes binary guard bars, payload encoding, and highlighted terminating check digit.
Step-by-Step Weight Multiplications
Sum of products (83) mod 10 = 3. Check Digit = (10 - 3) % 10 = 7
| Pos | Char | Weight | Product | Subtotal |
|---|
Batch Check Digit Calculator & Validator
Paste multiple numbers (one per line or comma separated) to compute or verify in bulk.
Batch Results:
Supported Check Digit Standards & Symbologies
Click any algorithm below to immediately load its configuration, sample data, and formula parameters.
Explore All Check Digit Subtools & Calculators
Dedicated standalone calculators, barcode verifiers, converters, and diagnostic suites across GS1, ISO, financial, and governmental symbologies.
Core Algorithms & Modulus
17 toolsCalculate or verify Modulus 10 digits.
Extend Luhn to custom character sets.
Calculate permutation-based check digits.
Calculate quasigroup-based check digits.
Apply alternating positional weights.
GS1 & Retail Barcodes
16 toolsSelect the applicable GTIN length. GS1
Complete eight-digit product identifiers.
Complete twelve-digit product identifiers.
Complete thirteen-digit product identifiers.
Complete fourteen-digit trade item identifiers.
Publishing & Identifiers
9 toolsCalculate numeric or X check characters.
Calculate thirteen-digit book identifier checks.
Convert eligible ISBNs and recalculate checks.
Convert eligible 978-prefix ISBNs.
Check serial publication identifiers.
Industrial & Barcode Symbologies
9 toolsCalculate optional Modulus 43 characters.
Calculate C and K characters.
Calculate the symbol check value.
Calculate MSI barcode check digits.
Apply the selected weighting variant.
Diagnostic, Analysis & Utilities
23 toolsCheck encoded Code 128 symbol values.
Append checks using a selected scheme.
Compare supplied and calculated check characters.
Recalculate an incorrect check field.
Isolate scheme-specific check characters.
Banking & Financial Standards
18 toolsCalculate international account check digits. SWIFT
Verify existing IBAN check digits.
Apply country-specific account rules.
Calculate US routing check digits.
Calculate domestic account control digits.
Government & Identity Numbers
22 toolsCalculate device identifier Luhn digits.
Check SIM identifier checksums.
Apply healthcare provider identifier rules.
Check NHS identifier control digits.
Verify Social Insurance Number checksums.
Transport, Shipping & Travel
8 toolsApply the applicable vehicle checksum rules.
Calculate freight-container check digits. BIC
Check international postal item identifiers. UPU
Check seven-digit ship identifier checksums.
Check European vehicle number digits.
How Check Digits Prevent Critical Transcription Errors
A check digit helps detect typing errors in a code, such as a barcode, account number or serial tag. An algorithm calculates one or more check digits from the rest of the code.
Single-digit Transcription Error Detection
Catches 100% of cases where an operator types one wrong digit (e.g. typing 5 instead of 6).
Adjacent Transposition Error Detection
Alternating weight patterns (such as 3 and 1) detect over 98% of accidentally flipped adjacent digits (e.g. typing 35 instead of 53).
Zero Network Roundtrip Overhead
Barcode optical scanners instantly validate codes offline before transmitting payload to checkout databases or warehouse management systems.
The GS1 Modulo 10 Algorithm Step-by-Step
- Count from right to leftMultiply the digit immediately preceding the check digit position by 3, the next by 1, the next by 3, continuing in an alternating 3-1-3-1 cadence.
- Sum all calculated productsAdd all resulting products together to obtain a cumulative total sum (e.g., \( S = 85 \)).
- Modulo 10 and subtractionDetermine remainder \( R = S \pmod{10} \). If \( R = 0 \), check digit is 0. Otherwise, check digit is \( 10 - R \).
Check Digit = (10 - (Sum of Weighted Products % 10)) % 10Frequently Asked Questions
Answers to common questions regarding check digits and barcode generation.
What is the difference between EAN-13 and UPC-A check digit calculation?
Both EAN-13 (13 digits) and UPC-A (12 digits) use the exact same GS1 Modulo 10 algorithm. In fact, any standard 12-digit UPC-A can be converted to an EAN-13 simply by prepending a leading 0 (zero), and the resulting check digit remains identical!
Can I generate barcodes for commercial products with this tool?
Yes! This tool calculates the official standard check digit specified by GS1. However, to sell items commercially in retail stores (Amazon, Walmart, supermarkets), your company prefix must be officially licensed through GS1. Once you have your licensed prefix and item numbers, this tool calculates the exact check digit you need.
How does the Luhn algorithm differ from GS1 Modulo 10?
While GS1 multiplies alternate digits by 3, the Luhn algorithm doubles (multiplies by 2) every second digit. If the doubled result exceeds 9, the two digits of the result are added together (or 9 is subtracted from it). Luhn is widely used for credit card validation (Visa, Mastercard, Amex) and cellular mobile IMEI numbers.
Does CheckDigitLab store or upload the numbers I enter?
No. All calculations, barcode visualizations, and batch verifications are executed entirely within your client's web browser using JavaScript. No card numbers, account details, or proprietary barcode sequences are ever sent to a remote server.