What Is a Mortgage Rate Lock? How It Works & What It Costs

TL;DR: A mortgage rate lock is a lender's written promise to hold your interest rate steady for a set window, typically 30 to 60 days, while your loan moves through underwriting and closing. If rates rise during that window, you're protected; if they drop, you may need a "float-down" option to benefit, and that usually costs an extra 0.125% to 0.25% of the loan amount. Locks that expire before closing can force a costly extension fee, often $250 to $500 or more depending on the lender.

_Last reviewed: August 2026 · 6 min read_

You found a rate you like, but closing is still weeks away and rates seem to move every day. A mortgage rate lock answers that worry directly: it freezes the number your lender quoted you, so what you see today is what you pay at closing, not whatever the market does in between.

Okoniq Property Hub helps homeowners track loan documents, lock expiration dates, and closing deadlines in one place so nothing slips through during the underwriting window.

How does a mortgage rate lock actually work?

A rate lock is a written agreement between you and your lender that fixes your interest rate for a specific number of days, most commonly 30, 45, or 60. Once locked, that rate doesn't move even if the broader market rate climbs before you close, as long as your loan terms (loan amount, credit score, property type) stay the same.

Lenders can lock a rate as soon as you have a signed purchase contract or, for a refinance, once your application is submitted. The lock is tied to specific loan parameters. If you switch loan programs, change the loan amount by a meaningful margin, or your credit score drops during underwriting, the lender can re-price the loan and the original lock may no longer apply.

Most locks are free for standard windows like 30 or 45 days. Longer locks, such as 60 or 90 days for new construction, usually carry a fee, often 0.25% to 0.5% of the loan amount, because the lender is taking on more market risk. If you're deciding between locking now versus waiting, it helps to first understand how mortgage points affect your rate, since some borrowers combine a lock with a points purchase to get an even lower number.

When should you lock your mortgage rate?

Lock as soon as you have a firm closing timeline and you're comfortable with the rate quoted, not before. Locking too early, before you have an accepted offer or a realistic closing date, risks the lock expiring before you actually close, which triggers extension fees.

A good rule: match the lock period to your expected closing date plus a 5 to 10 day buffer. A purchase with a 30-day contract-to-close timeline pairs well with a 45-day lock. Refinances, which can take longer due to appraisal scheduling and title work, often need a 45- to 60-day lock to be safe.

Rates can move 0.1% to 0.5% in a single week during volatile periods, so once you've compared offers and picked a lender, locking removes the guesswork. If you're weighing whether locking in now versus a variable option makes sense at all, it's worth reading when an adjustable-rate mortgage makes sense before committing to a fixed-rate lock strategy.

What happens if your rate lock expires before closing?

If your lock expires before you close, you'll either need to extend it for a fee or accept the current market rate, whichever your lender allows. Extension fees typically run $250 to $500, or a small percentage of the loan amount per week, depending on the lender's policy.

Delays that cause this are usually outside your control: a slow appraisal, a title issue, or a lender backlog. That's why it pays to ask your loan officer upfront what their extension policy costs and whether they'll cover fees caused by their own processing delays. Some lenders offer one free extension of 5 to 15 days as a courtesy; others charge from day one.

| | Rate Lock Expires (No Extension) | Rate Lock Extension | |---|---|---| | Cost | You accept current market rate | Typically $250-$500 or 0.125%-0.25% of loan | | Risk | Rate could be higher or lower | Locked rate is preserved | | Best for | Rates have dropped since your lock | Rates have risen or closing is delayed |

Keeping close track of your closing timeline against your lock expiration date is one of the simplest ways to avoid a surprise fee. This connects closely to reading your mortgage statement accurately once the loan closes, since the locked rate is what should appear on your very first statement.

Can you get a lower rate after locking (float-down options)?

Yes, but only if your lock includes a float-down provision, which most standard locks do not by default. A float-down lets you capture a lower rate if the market drops after you lock, usually for an added cost of 0.125% to 0.25% of the loan amount, sometimes waived on jumbo or premium loan products.

Without a float-down, a locked rate is a two-way street: you're protected from increases but you also can't benefit from decreases without breaking the lock or refinancing. If rates drop significantly right after you lock, comparing the cost of a float-down fee against a future refinance is worth doing with actual numbers. The refinance break-even calculation is the same math you'd use here: divide the float-down cost by your monthly savings to see how many months until it pays off.

What should you check before signing a rate lock agreement?

Confirm the lock period length, the exact rate and points, any extension fee schedule, and whether a float-down is included, all in writing before you sign anything. Verbal quotes from a loan officer are not binding; only the written lock confirmation, usually emailed or in your loan portal, protects you.

Also check whether the lock is tied to a specific lender-paid or borrower-paid points structure, since paying points changes the rate you're locking in. If you're buying points to reduce the rate, verify that both the points cost and the discounted rate are listed on the same lock document, not on separate paperwork that could get out of sync during underwriting.

FAQ

How long does a typical mortgage rate lock last?

Most rate locks run 30 to 60 days, with 30 and 45 days being the most common for standard purchase and refinance closings without complications.

Does locking a rate cost money?

Standard 30- to 45-day locks are usually free. Longer locks of 60 to 90 days, or locks with a float-down option, typically cost 0.125% to 0.5% of the loan amount.

Can a lender change my locked rate?

Only if your loan terms change materially, such as a lower credit score, a different loan amount, or a switch in loan program discovered during underwriting. Otherwise the locked rate holds through closing.

What happens if rates drop after I lock?

You keep your locked rate unless your agreement includes a float-down option, which lets you capture the lower rate for an added fee, usually 0.125% to 0.25% of the loan amount.

Is a rate lock the same as a rate quote?

No. A rate quote is an estimate that can change daily with the market. A rate lock is a binding written agreement that holds that specific rate for a set period.

This is educational information, not financial advice. Consult your loan officer or a licensed mortgage professional about the specific lock terms and fees on your loan.