ForHosting KIT · Developer Utilities

Home affordability calculator

This home affordability calculator estimates the highest purchase price supported by your income, recurring debts, available down payment, mortgage terms, ownership costs, and chosen debt-to-income limits.

● BetaFree · in your browser

Run — free How it works & API

Use it from WebAPIEmailTelegramApp soon

It evaluates both a housing-only ratio and a total-debt ratio, uses whichever creates the tighter monthly budget, and solves for a home price that includes principal, interest, property tax, homeowners insurance, and association dues. The result is a planning estimate, not a loan approval, appraisal, or recommendation to spend the maximum amount shown.

Build the monthly budget from both DTI limits

Affordability starts with gross monthly income, calculated by dividing gross annual household income by twelve. The front-end debt-to-income limit sets the share of that income available for the complete housing payment. The back-end limit sets the share available for housing plus existing required debt, so the calculator subtracts monthly obligations such as student loans, vehicle loans, personal loans, and minimum credit card payments. It then uses the lower of those two housing allowances. This matters because the binding constraint differs by household: someone with little existing debt may be limited by the front-end ratio, while someone with substantial obligations may be limited by the back-end ratio. Enter debts as required monthly payments, not outstanding balances, and do not include the proposed mortgage payment because that is what the calculation is solving. The returned limiting DTI field makes the decision visible. Your chosen ratios are scenario assumptions rather than universal lending rules. A lender may calculate qualifying income or debts differently, and a prudent personal budget may call for lower ratios than an underwriting program permits.

Turn the housing allowance into a maximum price

The monthly housing allowance must cover more than mortgage principal and interest. This calculator reserves the entered association dues, then accounts for property tax and homeowners insurance as annual percentages of the home price. The remaining relationship is solved together with the standard fixed-rate amortization formula, so price-based costs and the mortgage payment stay within one consistent monthly ceiling. The down payment reduces the loan principal dollar for dollar. If the available cash is large enough to avoid a loan within the calculated limit, the result uses only the amount of down payment needed for that price. A zero interest rate is supported with a direct principal-divided-by-payments formula instead of an unstable division. The model assumes equal monthly payments, a fixed rate, and a fully amortizing loan for the entire term. It does not include mortgage insurance, special tax assessments, utilities, maintenance, closing costs, lender fees, discount points, adjustable-rate changes, balloon payments, or interest-only periods. Add omitted recurring housing costs conservatively by increasing the monthly HOA input if you want them reserved inside the same budget.

Interpret the estimate without mistaking it for approval

Use the maximum home price as a comparison boundary for scenarios, not as a target that must be reached. Review the itemized monthly principal and interest, property tax, insurance, and association dues to see where the budget goes. Try a lower DTI limit to preserve room for repairs, savings, childcare, transportation, utilities, or changes in income. Compare interest rates to understand how financing conditions affect purchasing power, and test a larger down payment only after keeping closing costs and emergency reserves separate. Actual quotes can differ because taxes and insurance are property-specific, rates change, and lenders apply credit, documentation, reserve, occupancy, and loan-program requirements. The calculator also assumes the entire entered income qualifies and that every entered debt payment remains constant. A preapproval, inspection, insurance quote, and detailed cash-flow review are still necessary before making an offer. For repeatable automated analysis, the API price is $0.002 per request. The algorithm uses no network, randomness, or current date, so identical inputs produce identical results that can be stored and compared in an audit trail.

What you can do with it

Set a listing search ceiling

Estimate a price boundary before browsing homes, using a deliberate DTI target and realistic ownership costs.

Compare financing scenarios

Measure how a changed interest rate, loan term, or down payment affects the maximum supported purchase price.

Evaluate debt payoff

Compare current monthly obligations with a reduced debt payment to see which DTI constraint controls affordability.

FAQ

What does the calculation cost?

Each API request costs $0.002; the browser calculator is free to run.

What is included in the monthly housing payment?

The estimate includes mortgage principal and interest, percentage-based property tax and homeowners insurance, and the entered monthly association dues.

What debts should I enter?

Enter required recurring monthly payments for debts such as loans and credit cards. Exclude the proposed mortgage and use payments rather than balances.

Why does the calculator use two DTI ratios?

The front-end ratio limits housing expense alone, while the back-end ratio limits housing plus current debts. The tighter allowance controls the result.

Does the result guarantee mortgage approval?

No. It is a deterministic planning estimate, while lenders also consider credit, eligible income, reserves, appraisal, documentation, and program-specific rules.

Are closing costs included in the down payment?

No. The down payment is applied to the purchase price. Keep closing costs, moving expenses, and emergency reserves separate.

For developers — API access

Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.

API endpoint

POSThttps://api.kit.forhosting.com/finance/mortgage-affordability

Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.

Call it from your stack

curl -X POST https://api.kit.forhosting.com/finance/mortgage-affordability \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"annual_income":120000,"monthly_debts":750,"down_payment":60000,"annual_interest_rate":6.5,"loan_term_years":30,"front_end_dti":28,"back_end_dti":36,"annual_property_tax_rate":1.2,"annual_home_insurance_rate":0.35,"monthly_hoa":150}'

const res = await fetch("https://api.kit.forhosting.com/finance/mortgage-affordability", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "annual_income": 120000,
    "monthly_debts": 750,
    "down_payment": 60000,
    "annual_interest_rate": 6.5,
    "loan_term_years": 30,
    "front_end_dti": 28,
    "back_end_dti": 36,
    "annual_property_tax_rate": 1.2,
    "annual_home_insurance_rate": 0.35,
    "monthly_hoa": 150
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/finance/mortgage-affordability",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "annual_income": 120000,
    "monthly_debts": 750,
    "down_payment": 60000,
    "annual_interest_rate": 6.5,
    "loan_term_years": 30,
    "front_end_dti": 28,
    "back_end_dti": 36,
    "annual_property_tax_rate": 1.2,
    "annual_home_insurance_rate": 0.35,
    "monthly_hoa": 150
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/finance/mortgage-affordability", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"annual_income":120000,"monthly_debts":750,"down_payment":60000,"annual_interest_rate":6.5,"loan_term_years":30,"front_end_dti":28,"back_end_dti":36,"annual_property_tax_rate":1.2,"annual_home_insurance_rate":0.35,"monthly_hoa":150}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"annual_income":120000,"monthly_debts":750,"down_payment":60000,"annual_interest_rate":6.5,"loan_term_years":30,"front_end_dti":28,"back_end_dti":36,"annual_property_tax_rate":1.2,"annual_home_insurance_rate":0.35,"monthly_hoa":150}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/finance/mortgage-affordability", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "annual_income": 120000,
  "monthly_debts": 750,
  "down_payment": 60000,
  "annual_interest_rate": 6.5,
  "loan_term_years": 30,
  "front_end_dti": 28,
  "back_end_dti": 36,
  "annual_property_tax_rate": 1.2,
  "annual_home_insurance_rate": 0.35,
  "monthly_hoa": 150
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "finance.mortgage_affordability",
  "status": "queued",
  "_links": {
    "result": "/tasks/tsk_…/result"
  }
}

The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.

Pricing

Per request$0.002

Published price — no tokens, no invented credits. A failed task is never charged.

Errors

HTTP	Code	Meaning
`401`	`unauthorized`	Missing or invalid API key.
`402`	`insufficient_balance`	Your balance doesn't cover the task price.
`404`	`unknown_type`	That task type doesn't exist.
`429`	`rate_limited`	Too many requests. Use the webhook instead of polling.

Read the full KIT documentation →