A rate lock is a lender's guarantee that your interest rate and points will not change for a set window while your loan moves through underwriting, even if the broader market shifts. Most locks run 30, 45, or 60 days, and going past that window without closing can mean paying an extension fee or losing the locked rate entirely. Some lenders also offer a float-down option, letting you capture a lower rate if the market improves after you lock. Knowing these mechanics before you lock keeps a rate move from turning into a surprise at the closing table.
How it works
Locking freezes your rate and points combination as of the day you lock, based on your loan program, credit profile, and the lender's pricing that day. The lock period needs to comfortably cover the time from application to closing, a purchase with a tight timeline might use a 30-day lock, while a longer escrow calls for 45 or 60 days.
| Lock length |
Typical cost |
Best for |
| 15-30 days |
Often included free |
Fast closings, refinances |
| 45 days |
Small fee or built into rate |
Standard purchase timelines |
| 60+ days |
Higher fee or slightly higher rate |
New construction, longer escrow |
Longer locks generally cost more, either as an upfront fee or a slightly higher rate, because the lender is holding risk for a longer window.
Float-down options and what happens if you miss the window
A float-down lets you relock at a lower rate if the market improves before closing, usually for a fee or a slightly higher rate on the original lock. Without one, you are committed to the locked rate even if rates drop, you would need to cancel and restart with a new lender to capture a lower rate, which is rarely worth the cost and delay.
If your closing slips past the lock expiration, the lender typically offers an extension for a fee, or reprices the loan at current market rates if you decline. Delays on the buyer's side, like a slow appraisal or documentation, are the most common reason a lock expires before closing.
Steps to lock with confidence
- Confirm the lock period covers your realistic closing date, with a cushion for common delays like appraisal scheduling or underwriting conditions.
- Get the locked rate, points, and expiration date in writing. A verbal confirmation is not enough if a dispute comes up later.
- Ask whether a float-down is available and what it costs. Not all lenders offer one, and terms vary widely.
- Track your closing timeline against the lock expiration as the process moves along, and flag any delay to your loan officer immediately.
- Ask about extension costs before you need one. Knowing the fee in advance avoids a surprise if your closing slips by a few days.
Common mistakes
- Floating too long hoping for a better rate. Waiting without a lock exposes you to the market moving against you, sometimes right before closing.
- Assuming a float-down is free. It usually carries a fee or a slightly higher starting rate, confirm the terms before counting on it.
- Not accounting for realistic delays. Appraisal scheduling and underwriting conditions can push a closing back further than buyers expect.
- Locking before you have a purchase contract, on programs that do not allow it. Confirm with your lender when locking is actually permitted in your situation.
FAQ
Does locking a mortgage rate cost money?
Often not for standard lock periods, but longer locks can carry a fee or a slightly higher rate. Ask your lender for the specific cost at each lock length.
Can I lock a rate with more than one lender?
Yes, since a lock is not a loan commitment. Some buyers lock with two lenders to compare, though this adds effort and is not necessary for most.
What happens if rates drop after I lock?
Without a float-down option, you keep the rate you locked. With one, you may be able to relock at the lower rate, usually for a fee.
What if my closing is delayed past the lock expiration?
Most lenders offer an extension for a fee. Ask about this cost when you lock, not after you need it.
Where to go next
Once your rate is locked, the next decisions follow quickly. See mortgage points explained for buying down your rate further, compare loan terms with 15 vs 30 year mortgage, and check ARM reset explained if you are considering an adjustable rate instead of a fixed lock.