How Much House Can You Actually Afford? The DTI Math Explained

“How much house can I afford” is usually answered backward — starting from a home price and checking whether it fits, rather than starting from your actual income and debt and solving directly for what fits. The second approach is the one lenders themselves use, and it’s the one worth doing yourself before you start house-hunting.

The debt-to-income ratio, explained

Lenders cap your total housing payment (plus existing debt) at a percentage of your gross monthly income — the debt-to-income ratio, or DTI. Three widely-cited thresholds show up across almost every lending guideline:

The Mortgage Affordability Calculator lets you pick your own target within this range and solves directly for the maximum home price it supports — including a meter showing where your chosen target sits against these standard bands.

Working backward: from payment to loan amount

The same amortization formula that turns a loan amount into a monthly payment can be run in reverse — solving for the maximum loan amount a known maximum payment supports:

Existing debt matters more than people expect

DTI counts all debt obligations, not just the new mortgage — a car loan, student loan, or credit card minimum payment all eat directly into the room left for a housing payment at a fixed DTI target. This is exactly why paying down existing debt before house-hunting can expand your affordable range as much as, or more than, saving a larger down payment. The Debt-to-Income Calculator shows your current ratio directly.

The max affordable price isn’t the target price

A calculated maximum represents the outer edge of what a lender’s math supports — not necessarily a comfortable number. Many financial advisors suggest targeting meaningfully under the calculated ceiling, leaving room for savings, emergencies, and other goals the DTI formula alone doesn’t account for.

Renting vs. buying at your affordable price

Once you know your affordable range, the next real question is often whether buying at that price beats renting for your specific timeline — appreciation, equity, and selling costs all factor in, which is exactly what the Rent vs Buy Calculator compares directly. And if you’re weighing a smaller home now against tapping equity later for a renovation or move-up purchase, the Home Equity Calculator shows how that equity accumulates over time.