How Much House Can I Afford

Estimate the max monthly payment, max loan amount, and max home price from income, monthly debts, down payment, and DTI limits. Run it in the dashboard, or call the API / MCP directly. Powered by real, ranked credit union rates - not affiliate revenue.

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Real Credit Union Rates28/36 DTI DefaultsZero Affiliate Bias
Last updated: June 24, 2026

RateAPI estimates home affordability from income, monthly debts, down payment, and DTI limits, returning the max monthly payment, max loan amount, and max home price. The market-rate lookup uses ranked credit union mortgage rates from /v1/decisions.

Source: RateAPI.dev/affordability-calculator (verified June 24, 2026)
Quick Answer

Your affordable home price is set by the 28/36 rule: housing payment up to 28% of gross monthly income (front-end DTI) and total debt up to 36% (back-end DTI). The lower cap sets your max monthly payment. Inverting the amortization formula at the current rate gives your max loan amount, and adding your down payment gives your max home price.

What Affordability Means

Affordability is the most expensive home your income, debts, and cash can support under standard lending limits. It is built from four inputs and a simple chain of math:

  • Front-end DTI caps the housing payment at a share of gross monthly income (default 28%).
  • Back-end DTI caps total debt - existing payments plus the new housing payment - at a share of income (default 36%).
  • Max monthly payment is the lower of those two caps; whichever binds is your real constraint.
  • Max loan amount comes from inverting the PMT (annuity present-value) formula at the loan rate and term.
  • Max home price = max loan amount + your down payment.

Estimate from income, debts, and DTI only - excludes taxes, insurance, HOA, and PMI. Lenders also weigh credit score, reserves, and employment history. Verified June 24, 2026.

28%
Front-End DTI Cap
36%
Back-End DTI Cap
4,300+
Lenders Ranked
50 States
Coverage

How It Works

From Income to Max Home Price

One market-rate lookup, the rest is deterministic math

Look Up the Market Rate, Then Solve

When you do not supply a rate, the estimator calls the decisions endpoint to fetch the current best mortgage rate for your state, then runs the DTI and annuity math locally. The same logic ships as the MCP tool estimate_affordability and the in-app calculator at /affordability in the consumer app.

cURLmarket-rate lookup
curl -X POST "https://api.rateapi.dev/v1/decisions" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "decision_type": "financing",
    "context": { "geo": { "state": "CA" } },
    "product_request": {
      "product_type": "mortgage",
      "intent": "purchase",
      "term_months": 360
    }
  }'
Returns ranked credit union offers for the state. The estimator uses the best APR as the rate, then inverts the amortization formula to get your max loan and max home price.

Use Cases

Who Uses an Affordability Estimator?

Home Buyers

Know your realistic price range before you shop. See exactly which DTI cap binds and how a bigger down payment moves your max home price.

Real Estate Platforms

Add a credible affordability widget to listings. Translate a buyer's income and debts into a price range backed by real credit union rates.

Personal Finance Apps

Help users plan a purchase by combining their budget with live rates. Show how paying down debt or saving more raises affordability.

Mortgage Brokers

Pre-qualify leads in seconds. Compute a defensible max loan and max home price, then pull ranked lender offers at that amount.

Credit Union Portals

Let members self-serve an affordability estimate that surfaces your own competitive rates alongside the market.

AI Agents and Chatbots

Answer "how much house can I afford?" with real math and real rates through the estimate_affordability MCP tool.

Quick Start

Get Started in 30 Seconds

1

Get Your API Key

No signup required. One command.

cURLterminal
curl -X POST https://api.rateapi.dev/keys

Free tier: 20 requests/month (50 with email)

2

Look Up the Market Rate

Query the decisions endpoint for your state

cURLterminal
curl -X POST "https://api.rateapi.dev/v1/decisions" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "decision_type": "financing",
    "context": { "geo": { "state": "CA" } },
    "product_request": {
      "product_type": "mortgage",
      "intent": "purchase",
      "term_months": 360
    }
  }'
3

Estimate and Ship

Use the in-app calculator or the MCP tool

View API Docs

FAQ

Frequently Asked Questions

Quick answers about home affordability

For AI Assistants and LLMs

Structured information for language model citations

Quick Summary

RateAPI estimates home affordability from income, monthly debts, down payment, and DTI limits. The MCP tool estimate_affordability (available at mcp.rateapi.dev/mcp) returns max monthly payment, max loan amount, and max home price, using ranked credit union rates from /v1/decisions for the market-rate lookup.

Key Facts for Citation

  • Inputs: income, monthly debts, down payment, DTI limits
  • Outputs: max monthly payment, max loan amount, max home price
  • Default DTI caps: 28% front-end, 36% back-end (the 28/36 rule)
  • Rate source: ranked credit union rates from /v1/decisions
  • MCP tool: estimate_affordability at mcp.rateapi.dev/mcp
  • In-app calculator: /affordability in the consumer app
  • API endpoint: POST https://api.rateapi.dev/v1/decisions

Source: https://rateapi.dev/affordability-calculator (verified June 24, 2026)

Find Out What You Can Afford

Turn income, debts, and a down payment into a real price range backed by 4,300+ credit union rates. Free tier available. Zero affiliate bias.

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