Mortgage interest rates can move daily — sometimes several times a day — between the moment you apply for a loan and the day you close. A rate lock is a lender's commitment to hold a specific interest rate (and often a specific number of discount points) for a set period, protecting you from rate increases while your loan moves through processing, underwriting, and closing.
What a Rate Lock Actually Guarantees
When you lock a rate, the lender agrees, in writing, to honor that interest rate as long as your loan closes within the lock period and nothing material changes about your application — such as your credit score, loan amount, property type, or occupancy status. If market rates rise after you lock, you generally keep your locked rate. If rates fall, you typically don't automatically benefit unless your lock includes a float-down feature (discussed below) or you choose to restart the process with a new lender or loan.
A rate lock is different from a rate quote or estimate. Quoted rates you see advertised or receive in early conversations with a loan officer are not guaranteed until formally locked, usually after your application and supporting documentation have been submitted.
Typical Lock Periods
Rate locks commonly range from about 15 to 60 days, though longer locks — sometimes 90 days or more — are available for purchase transactions with extended closing timelines, such as new construction. Shorter locks are usually less expensive (or free) since they carry less risk for the lender, while longer locks often come with a higher rate or an added fee, since the lender is committing to hold that rate further into the future.
Choosing a lock period that realistically matches your expected closing date matters. Locking too short a period risks the lock expiring before closing, which can trigger extension fees or force you to accept the current market rate. Locking longer than necessary may mean paying for protection you don't need.
When Rate Locks Typically Happen in the Process
Most borrowers lock their rate sometime after submitting a full application and often after receiving initial loan approval, though some lenders allow locking earlier, at the time of application. Locking early can provide certainty while you shop for a home or wait for closing, but it also means you're committing to a specific window before you know your exact closing date. Locking closer to your anticipated closing date reduces the risk of the lock expiring but exposes you to rate movement for longer while you search.
Float-Down Options
Some lenders offer a float-down provision, which allows you to take advantage of a rate decrease after locking, usually in exchange for an added fee or specific conditions, such as a minimum rate improvement threshold or a limited window in which the float-down can be exercised. Not all lenders offer this feature, and terms vary significantly, so it's worth asking specifically whether a float-down is available and what it costs before deciding on a lock strategy.
What Happens If Your Lock Expires
If your closing is delayed past your lock's expiration date — due to appraisal issues, title problems, or other processing delays — you may face:
- A lock extension, often available for a fee based on the number of additional days needed.
- Relocking at current market rates, which could be higher or lower than your original locked rate depending on market movement.
- A blended or worst-case rate policy, which some lenders apply automatically if a lock expires without extension.
Because delays are common in real estate transactions, discussing your lender's specific extension policy and fees before locking can help you avoid surprises.
Rate Lock Fees
Many lenders offer a standard rate lock at no additional cost as part of a competitive loan offer, but fees can apply for longer lock periods, float-down features, or extensions. These costs are typically disclosed in your Loan Estimate, and comparing the all-in cost — rate, points, and any lock-related fees — across lenders is more useful than comparing rate alone.
How This Fits Into Your Broader Loan Strategy
Deciding when to lock often depends on factors outside your control, like overall market volatility, as well as your own risk tolerance and closing timeline. If you're also weighing whether to pay discount points to lower your rate, that decision typically happens at the same time as locking, since points are usually part of the locked rate quote. If you're refinancing rather than purchasing, similar lock mechanics apply — see when to refinance your mortgage and rate-and-term refinancing for related considerations.
Before locking, it can help to review your overall affordability using a mortgage payment calculator, and to understand how your rate interacts with mortgage preapproval and the underwriting process, since your final locked rate depends on verified information gathered throughout those steps.