What is a mortgage rate lock and when should I lock?

A rate lock is an agreement with your lender that your interest rate will not change for a set number of days, no matter what happens to rates in the market.

It gives you certainty that the payment you planned on will be the payment you get at closing.

Rate locks are typically offered in 30, 45, or 60 day windows. Longer locks usually cost a little more or carry a slightly higher rate.

The right length covers your closing timeline with a little cushion, without paying for months you do not need.

Most lenders lock the rate once you have an accepted purchase contract and a closing date, because that gives a clear window to underwrite and close the loan.

Some lenders offer a lock earlier or allow you to pay to extend it, so it is worth asking about your options.

If your closing runs past the lock date, your rate could expire and the lender may charge to extend the lock or offer the current rate, which may be higher.

Keeping your documents ready and responding quickly reduces the chance of a delay that costs you.

Floating means leaving your rate unlocked in hopes it drops before closing, which carries risk if rates rise instead.

Locking gives you certainty, which matters most to buyers who are building a budget around a specific payment.

Ask how long the lock lasts, what it costs to extend, whether you can relock at a lower rate if rates drop, and what happens if closing is delayed.

Clear answers to these questions take the guesswork out of your rate and your payment.