What is a mortgage rate lock and how long should mine be?
A rate lock freezes your quoted rate for a set number of days while your loan is processed, protecting you if the market moves against you. Longer locks cost more, so the right length is the shortest one that comfortably covers your closing date — with enough margin that you are not paying to extend it.
Mortgage pricing moves with the bond market, daily and sometimes intraday. Between the day you are quoted and the day you close, the rate could move either way. A lock removes that uncertainty in one direction: the lender commits to honour the quoted rate for an agreed window, provided you close inside it.
Choosing the length
Common windows are 30, 45 and 60 days. Longer costs more, because the lender is carrying the risk for longer, and that cost shows up as a slightly worse rate or a lock fee.
The trap is locking too short. A 30-day lock on a purchase that realistically needs 40 days means paying for an extension — usually more than the longer lock would have cost at the outset. Ask what is realistic for your loan type and your market, then add a margin.
Rates move, and locks are one-directional
If rates fall after you lock, you are held at the higher rate unless your lock includes a float-down. Some lenders offer one, often for a fee or with conditions on how far rates must fall. Ask before you lock, not after.
What breaks a lock
Locks are tied to the loan as described when it was issued. Change the loan amount, the product, the property or the down payment materially and the lock can be re-priced. So can a significant change in your credit or income during processing. This is the reason lenders ask borrowers not to open new credit accounts before closing.
Comparing locked quotes
A quote is only comparable against another quote with the same lock period. A lender quoting on a 15-day lock will look better than one quoting on 45 days, and the difference is not a better deal — it is a shorter promise.
Related questions
Does locking a rate cost money?
Often it is built into pricing rather than charged separately, but longer locks are always paid for one way or another. Extensions are usually charged explicitly, per day or in blocks.
Can I switch lenders after locking?
Yes — a lock is not a binding commitment to borrow. But you would restart processing, and any application fees already paid are generally gone.
What happens if my lock expires before closing?
You either extend, at a cost, or re-lock at whatever the market is offering that day. Neither is good, which is why the lock length should be set from a realistic closing timeline rather than an optimistic one.