15-year vs 30-year mortgages

Same principal and the same rate, a shorter term raises the payment and cuts total interest. In the market the rates are usually not the same.

Finance Calculator Pro team·Updated October 14, 2026·4 min read

What the term changes in the formula

The amortizing payment has n in it. Cut n from 360 months to 180 and M rises, even if r is unchanged, because the same principal must be retired in half the scheduled months. Interest is still only charged on the remaining balance, so you also spend fewer months paying interest on a large balance.

M = P × r / (1 − (1 + r)^−n)

Run both terms on the mortgage calculator. If the question is “what if I keep the 30-year note and send extra,” use the payoff calculator instead: extra principal on a 30-year is not the same contract as a 15-year note.

The rate is usually not the same

Lenders price 15-year and 30-year products separately. FRED publishes a 30-year fixed average (MORTGAGE30US). The Federal Reserve’s H.15 release is the broader selected-rate publication. This site will not invent a typical spread between 15-year and 30-year quotes. Look up both products on a current rate sheet or a Loan Estimate pair. A smaller 15-year rate makes the payment gap narrower than the same-rate comparison above and makes the interest gap wider.

Points, credits, and lock costs also differ by product. A comparison that ignores them is a payment comparison, not a cash-to-close comparison. The CFPB compare workflow is built for that document-level work.

Liquidity and the payment you must make

A 15-year note raises the amount you are required to send. Missing that payment has the same servicing consequences as missing a smaller 30-year payment. A 30-year note with voluntary extra principal keeps the lower required payment and lets you skip the extra in a thin month. That flexibility is the usual argument for taking the longer term and prepaying when you can. It is also how people stay on the high-interest path if the extra never happens.

Affordability underwriting looks at the required payment, not at a hoped-for extra. The affordability calculator sizes a price from a payment cap. Switching the term from 30 to 15 in that tool lowers the price the same income can support, because the P&I for a given loan is higher.

Refinancing from one term to the other

Replacing a 30-year with a 15-year is a refinance, not a setting on the old note. You will pay closing costs and start a new amortization. The refinance calculator will often show a higher new payment and still a large lifetime interest cut, with a cash break-even that depends on costs. Replacing a 15-year with a 30-year does the reverse: payment relief, more scheduled interest, and a term reset that can erase years of principal progress if the new balance is not much smaller.

Ability-to-repay rules in 12 CFR 1026.43 still apply to the new loan. A payment you prefer is not the same as a payment a lender must approve.

Taxes, PMI, and other side effects

More principal each month means less interest in later years, which can change a mortgage-interest deduction if you itemize and the interest is qualified under IRS Publication 936. That is not a reason by itself to pick a term. PMI, when present, is about loan-to-value, not about 15 versus 30; a faster principal drop can reach a cancellation threshold sooner. The CFPB’s PMI-removal page describes the 80% request and 78% automatic paths under the Homeowners Protection Act.

What this guide will not claim

It will not say which term is better. It will not cite an average savings percentage, an average 15-year discount, or a share of borrowers who pick each term. Those figures change, and this site does not run that survey. Compare two Loan Estimates, or two runs of the mortgage calculator with the rates you were actually quoted.