calculateVerifier()

Calculates the verifier digit for a given RUT body using the Modulo 11 algorithm.

Basic Usage


import { calculateVerifier } from 'rut.ts'
 
calculateVerifier('12345678')  // '5'
calculateVerifier('24657622')  // 'K'

Type Signature


function calculateVerifier(rutBody: string): VerifierDigit
function calculateVerifier(rutBody: string, options: { throwOnError: false }): VerifierDigit | null
function calculateVerifier(rutBody: string, options: { throwOnError: true }): VerifierDigit
 
type VerifierDigit = '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' | 'K'

Parameters

rutBody (string) - The RUT body (7-8 digits, without verifier)
options (optional) - Configuration options
- throwOnError (boolean, default: true) - If false, returns null instead of throwing

Return Value

Returns VerifierDigit or null:

A single character: '0' to '9' or 'K'
null if invalid (only in safe mode)

Algorithm

The function implements the Modulo 11 algorithm:

Take the RUT body digits
Multiply each digit by factors (2,3,4,5,6,7,2,3,4…) from right to left
Sum all products
Calculate 11 - (sum % 11)
If result is 11, verifier is '0'
If result is 10, verifier is 'K'
Otherwise, verifier is the result as a string

Examples

Basic Calculation


import { calculateVerifier } from 'rut.ts'
 
// Numeric verifiers
calculateVerifier('12345678')  // '5'
calculateVerifier('18972631')  // '7'
calculateVerifier('11111111')  // '1'
 
// K verifier (when result is 10)
calculateVerifier('24657622')  // 'K'
calculateVerifier('14625621')  // 'K'

Building a Complete RUT


import { calculateVerifier, format } from 'rut.ts'
 
const body = '12345678'
const verifier = calculateVerifier(body)
const completeRut = format(body + verifier)
 
console.log(completeRut)  // '12.345.678-5'

Safe Mode


import { calculateVerifier } from 'rut.ts'
 
// Without safe mode (throws)
try {
  calculateVerifier('123')  // Too short
} catch (error) {
  console.error(error)
}
 
// With safe mode (returns null)
const result = calculateVerifier('123', { throwOnError: false })
console.log(result)  // null
 
// Useful for form validation
const handleBodyInput = (body: string) => {
  const verifier = calculateVerifier(body, { throwOnError: false })
  if (verifier) {
    console.log(`Complete RUT: ${body}-${verifier}`)
  } else {
    console.log('Invalid body length or format')
  }
}

Input Flexibility


import { calculateVerifier } from 'rut.ts'
 
// Accepts formatted input (dots/hyphens removed)
calculateVerifier('18.972.631')  // '7'
calculateVerifier('18-972-631')  // '7'
 
// Handles leading zeros
calculateVerifier('018972631')  // '7' (zeros removed)

Validation Rules

The function validates:

✅ Body must be 7-8 digits after cleaning leading zeros
✅ Only numeric characters allowed (no K in body)
✅ Formatting characters (dots, hyphens) are automatically removed

Use Cases

✅ Generate custom RUTs with specific body numbers
✅ Verify RUT correctness by recalculating verifier
✅ Build RUT generation tools
✅ Educational purposes (demonstrate Modulo 11)
✅ Testing and debugging RUT validation

Understanding the Algorithm

Example calculation for body 12345678:


Step 1: Reverse digits and multiply
8×2 + 7×3 + 6×4 + 5×5 + 4×6 + 3×7 + 2×2 + 1×3
= 16 + 21 + 24 + 25 + 24 + 21 + 4 + 3
= 138

Step 2: Calculate modulo
138 % 11 = 6

Step 3: Get verifier
11 - 6 = 5 ✅

validate() - Validate complete RUT
generate() - Generate random valid RUTs
decompose() - Extract body and verifier