# Luhn Checksum Calculator Validate or generate numbers using the Luhn algorithm (mod-10). Works for credit cards, IMEI, IMEISV, SIN, NPI and any custom Luhn-based identifier. > Canonical page: https://elysiatools.com/en/tools/luhn-checksum - **Category:** Validation - **Keywords:** luhn, checksum, mod-10, credit card, imei, validator, generator, check digit ## Overview The Luhn Checksum Calculator allows you to validate or generate numbers using the Luhn algorithm (mod-10). It supports standard identifiers such as credit cards, IMEI, IMEISV, Social Insurance Numbers (SIN), National Provider Identifiers (NPI), and custom Luhn-based numbers, ignoring spaces and dashes automatically. ## Inputs - **Mode** (select) - **Number to Validate** (text): Any Luhn-based number. Separators are ignored. - **Total Length** (number): Total digit count including the check digit. - **Prefix (optional)** (text): Lock the leading digits of the generated number. ## When to use - When you need to verify if a credit card number, IMEI, or NPI is syntactically valid before processing it. - When generating mock test numbers with valid check digits for software testing and QA environments. - When calculating the correct check digit for a custom sequence of numbers that uses the mod-10 Luhn algorithm. ## How it works - Select the mode: either 'Validate' to check an existing number or 'Generate' to create a new one. - For validation, enter the number; the tool strips non-digit characters and computes the mod-10 checksum. - For generation, specify the desired total length and an optional prefix to lock the leading digits. - The tool instantly outputs the validation status or the generated number with its correct check digit. ## Use cases - Validating user-entered credit card numbers in a checkout form mock-up to ensure basic format correctness. - Generating a batch of valid IMEI numbers for testing mobile device registration systems. - Calculating the final check digit for custom internal membership or inventory tracking numbers. ## Frequently asked questions ### What is the Luhn algorithm? It is a simple checksum formula (mod-10) used to validate a variety of identification numbers, protecting against accidental typing errors. ### Does this tool store the credit card or IMEI numbers I enter? No, all calculations are performed locally in your browser, and no sensitive data is sent to any server. ### Can I generate numbers with specific prefixes? Yes, you can set an optional prefix, such as 4 for Visa or 35 for JCB, to lock the leading digits of the generated number. ### How does the tool handle spaces or dashes in the input? The calculator automatically ignores spaces, dashes, and other non-digit separators during validation. ### Does a valid Luhn checksum mean a credit card is active? No, it only confirms the number is mathematically valid. It does not verify account status, balance, or active status with the issuer. ## Related tools - [ICCID Generator](https://elysiatools.com/en/tools/iccid-generator): Generate valid ICCID numbers for SIM cards with proper Luhn checksums - [Credit Card Validator](https://elysiatools.com/en/tools/credit-card-validator): Validate credit card numbers and identify card type (Visa, MasterCard, UnionPay, etc.) - [CUSIP Validator](https://elysiatools.com/en/tools/cusip-validator): Validate 9-character CUSIP North American securities identifiers with mod-10 check-digit verification, issuer base and issue-number breakdown. - [ICCID Validator](https://elysiatools.com/en/tools/iccid-validator): Validate ICCID numbers for SIM cards with Luhn checksum and issuer analysis - [ISBN Validator](https://elysiatools.com/en/tools/isbn-validator): Validate ISBN-10 and ISBN-13 book number formats with checksum verification - [ISIN Validator](https://elysiatools.com/en/tools/isin-validator): Validate International Securities Identification Numbers (ISO 6166 ISIN) with Luhn check-digit verification, country/issuer prefix and NSIN breakdown. - [SEDOL Validator](https://elysiatools.com/en/tools/sedol-validator): Validate 7-character UK/Irish SEDOL securities identifiers with weighted mod-10 check-digit verification and SEDOL-7 structure breakdown. - [Tracking Number Validator](https://elysiatools.com/en/tools/tracking-number-validator): Identify and validate tracking numbers from FedEx, UPS, DHL, USPS, SF Express (顺丰) and other major carriers ## Samples - [Android Image Processing Java Samples](https://elysiatools.com/en/samples/android-image-processing-java): Android Java image processing examples including reading/saving images, scaling, and format conversion - [Android Image Processing Kotlin Samples](https://elysiatools.com/en/samples/android-image-processing-kotlin): Android Kotlin image processing examples including reading/saving images, scaling, and format conversion - [Web Image Processing Python Samples](https://elysiatools.com/en/samples/web-image-processing-python): Web Python image processing examples using PIL/Pillow including reading, saving, resizing, and format conversion - [Web Image Processing Rust Samples](https://elysiatools.com/en/samples/web-image-processing-rust): Web Rust image processing examples including image read/save, scaling, and format conversion ## Related content - [Check Digit, Checksum, and Identifier Validation Tools](https://elysiatools.com/en/hubs/check-digit-checksum-validation): Validate Luhn, Mod-11, GTIN, ISBN, IMEI, ICCID, VIN, IBAN, and ISIN codes in one focused hub for checksum-driven identifier checks. - [Identifier, Config, and Input Validation Tools](https://elysiatools.com/en/hubs/validation-validate): Compare validators for email, phone, IP, dates, cron, barcodes, payment details, env files, and other real-world inputs in one hub. - [Identifier, Address, and Code Format Validators](https://elysiatools.com/en/hubs/validation-format): Curated tools for identifier, address, account, and code format validation in one hub. - [JSON Schema and API Contract Validation Tools](https://elysiatools.com/en/hubs/json-validate): Compare JSON schema validation, OpenAPI response checks, mutation testing, stress testing, and breaking-change detection tools in one hub for API contract review.