US mortgage & home-finance calculators

What makes a US mortgage different

Four structural features separate the US from every other market on this site, and each one changes what you should be comparing when you shop for a loan.

The 30-year fixed rate is the default, and it is unusual. A UK borrower fixes for two or five years and then faces a repricing. A US borrower can fix for the entire life of the loan, which removes the single largest risk other markets carry. It is worth knowing how rare that is: most countries do not offer it, and it exists here because of how US mortgages are packaged and sold on rather than because lenders are generous.

Your rate does not follow the Federal Reserve. Thirty-year mortgage pricing tracks the 10-year Treasury yield plus a lender spread. Those move on expectations, so the Fed can hold or cut while mortgage rates rise the same day, which has happened. Waiting for a Fed cut is watching the wrong number, and the Freddie Mac weekly survey is the figure that matters.

PMI is a real cost with a defined end. Below 20% down you pay private mortgage insurance, and unlike interest it stops. Under the Homeowners Protection Act of 1998 you may request cancellation at 80% of the original value and the lender must terminate it automatically at 78%. Those two dates are typically eleven months apart, nobody writes to tell you the first one has arrived, and the gap is worth thousands.

The payment quoted is rarely the payment charged. Property tax is set at county level and homeowners insurance varies by state, and both are usually collected monthly into escrow alongside principal and interest. That total is PITI, and it is what a lender assesses you against.

The mistake that costs people a house

Lenders apply the front-end ratio to PITI, not to principal and interest. Most calculators show principal and interest only, so a buyer budgets against the smaller number and is surprised by the approval.

On a $9,000 monthly income at a 28% front-end limit, $2,520 is available for the whole housing payment. Budgeting with a principal-and-interest figure suggests a loan around $392,000. Once tax, insurance and PMI come out of that $2,520 first, about $1,767 remains for principal and interest, which supports roughly $275,000. That is a difference of about $117,000 in what a lender will advance, from the same income on the same day, and it is entirely a consequence of which figure you started from.

Debt-to-income, and what the rule actually is

The commonly cited 28/36 guideline is lender convention rather than law. The Consumer Financial Protection Bureau replaced the hard 43% Qualified Mortgage DTI cap with a price-based test in 2021, so there is no single statutory ceiling to point at, and individual lenders apply their own limits.

What holds regardless is the arithmetic of existing debt. Because the ratio is applied to your total monthly obligations, a payment you already make reduces your borrowing capacity by far more than its size suggests. A $500 monthly car payment costs roughly $78,000 of mortgage capacity at current rates, which is about $15,500 for every $100 of monthly commitment. Clearing one loan often moves the number further than a raise of the same amount, because a raise is taxed and a cleared payment is not.

Closing costs and points

Closing costs are a genuine second deposit, typically running to several percent of the purchase price across origination, appraisal, title, recording and prepaid escrow. They are separate from the down payment and are due at closing.

Discount points let you buy the rate down by paying cash upfront, which is a break-even calculation rather than a discount. The same logic applies in reverse to a lender advertising no origination fee: the fee is usually recovered in the rate, so the question is how long you hold the loan. Median US homeowner tenure is about 12 years, which is long enough that paying a fee upfront frequently wins.

Where the calculators fit

The mortgage calculator produces the full PITI figure rather than principal and interest alone, because that is the number a lender uses. The PMI calculator gives the rate by loan-to-value band, how long you pay it and both cancellation dates. The debt-to-income calculator applies the front-end and back-end ratios to your own obligations. The closing cost calculator covers the second deposit, and the points calculator handles the break-even.

Every figure is computed from the underlying formula rather than repeated from another site, and each rate used in an example carries its source and the date it was checked.