What is a mortgage rate lock?

When you apply for a mortgage, the interest rate quoted at application is not guaranteed — it moves with the market daily. A rate lock is the mechanism that freezes your rate once you've found a home and chosen a lender. The CFPB describes a rate lock as a lender's written commitment to hold a specific rate and points for a defined period, so the terms don't change before closing.

How long does a rate lock last?

Standard rate lock periods are 30, 45, or 60 days. Longer locks cost more — typically in the form of a higher rate or an upfront fee. If your closing is delayed beyond the lock expiration, you may have to pay an extension fee or re-lock at the current (possibly higher) market rate. Ask your lender what extensions cost before choosing a lock period.

• 30-day lock — standard for quick closes; cheapest option if you're confident in your timeline.
• 45-day lock — common for purchase transactions with moderate complexity.
• 60-day lock — used for new construction or complex loan files where the close date is uncertain.
• Extension fees — typically 0.125%–0.25% of the loan amount per 15-day extension period.

Float-down options

Some lenders offer a float-down option: if rates drop by more than a specified amount after you lock, you can capture a lower rate once. Float-downs typically cost 0.5%–1% of the loan amount as an upfront fee. They make sense if rates are volatile and expected to fall. Not all lenders offer them, so ask explicitly during rate shopping.

When should you lock?

Most borrowers lock once they are under contract on a home and have completed their lender selection. Locking too early (before a signed purchase agreement) wastes the lock window. Waiting too long risks rates rising before closing. The CFPB's Owning a Home rate checker helps you track real rate ranges so you can judge market timing.

How much a lock actually protects against

Rates move enough week to week that locking is not a formality. Freddie Mac's Primary Mortgage Market Survey put the national average 30-year fixed rate at 6.65% for the week of August 20, 2026 — down from 6.67% the prior week — while the 15-year fixed averaged 5.95%, against roughly $13.1 trillion mortgage loans outstanding nationwide (New York Fed, Q2 2026). A quarter-point swing changes the monthly payment by roughly $60–$65 on a typical loan size; that's the exposure a lock removes for the 30–60 days your file is in process. Loan size raises the stakes further once you cross FHFA's 2026 baseline limit of $832,750 conventional loans in most counties — jumbo files above that line often carry their own, sometimes pricier, lock terms. Check the current PMMS reading against the rate your Loan Estimate quotes before deciding whether a longer, costlier lock period is worth it.