Car affordability (20/4/10 rule) API

Apply the 20/4/10 rule (20% down, <=4yr term, <=10% gross on vehicle costs) and the loan-payment formula P=pmt*(1-(1+r)^-n)/r to solve the max affordable car price, financed amount, and a down-payment check. Answers 'what car can I afford on $5000/mo', 'max car price with $3000 down', 'how much car at 7% over 48 months'.

Price$0.01per request

MethodPOST

Route/v1/calc/budget-car-affordability

StatusLive

MIME typeapplication/json

Rate limit120/minute

CacheNo cache

budgetcarautoaffordabilityloan20-4-10calculatormoney

API URLhttps://x402.hexl.dev/v1/calc/budget-car-affordability

Integration docs

Example request

{
  "grossMonthlyIncome": 5000,
  "downPayment": 3000,
  "annualRate": 7,
  "termMonths": 48,
  "monthlyInsurance": 100
}

Example response

{
  "grossMonthlyIncome": 5000,
  "monthlyVehicleBudget": 500,
  "maxLoanPayment": 400,
  "monthlyInsurance": 100,
  "maxFinancedAmount": 16704.08,
  "downPayment": 3000,
  "maxCarPrice": 19704.08,
  "termMonths": 48,
  "annualRatePercent": 7,
  "rule": "20/4/10 (20% down, <=4yr term, <=10% gross on vehicle costs)",
  "rating": "meets 20% down rule"
}

Input schema

{
  "type": "object",
  "required": [
    "grossMonthlyIncome"
  ],
  "properties": {
    "grossMonthlyIncome": {
      "type": "number",
      "description": "Gross monthly income in dollars",
      "examples": [
        5000
      ]
    },
    "downPayment": {
      "type": "number",
      "description": "Down payment in dollars",
      "examples": [
        3000
      ]
    },
    "annualRate": {
      "type": "number",
      "description": "Loan APR percent (default 7)",
      "examples": [
        7
      ]
    },
    "termMonths": {
      "type": "number",
      "description": "Loan term in months (default 48)",
      "examples": [
        48
      ]
    },
    "monthlyInsurance": {
      "type": "number",
      "description": "Monthly insurance cost in dollars",
      "examples": [
        100
      ]
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}