Two Calculators, Two Different Questions
Most home-buying sites offer both, label them similarly, and leave you to figure out which to use. Here is the difference, stripped of marketing language.
Mortgage Calculator
Asks: "If I buy this $450,000 house with 20% down at 6.75% for 30 years, what is my monthly payment?"
Answers: A single monthly number, usually broken down into P&I, tax, insurance.
When to use it: You have already found the house, you know the price, and you want to know the payment before you make an offer.
Affordability Calculator
Asks: "Given my income of $110,000, monthly debts of $400, and a goal of staying within 33% DTI, what is the maximum home price I should be looking at?"
Answers: A maximum price ceiling plus the monthly payment at that ceiling.
When to use it: Before you start house hunting. Before you look at a single listing. Before you get pre-approved.
The Order That Actually Works
1. Affordability calculator first. Set your ceiling. 2. Pre-approval letter second. Banks will often approve you for more than your ceiling. Ignore the inflated number. 3. Shop for homes 10–15% below your ceiling. This leaves room for bidding-war adjustments without exceeding your ceiling. 4. Mortgage calculator last. Once you find a specific home, run it through the mortgage calculator to confirm the payment.
Using the mortgage calculator first is backwards — you will fall in love with a payment that fits, then realize you are locked into a home price that does not.
What Our Tool Does
The House Afford calculator is an affordability calculator, not a mortgage calculator. It solves for the maximum home price that keeps your DTI inside the 28/36 rule caps. For a mortgage payment calculator, check any of our FAQ links.