Mortgage Rate Locks Explained: When to Lock and What Happens If Rates Move
By Daniel Ramirez
Key Takeaways
- A mortgage rate lock is a lender's commitment to honor a specific interest rate for a set period, typically 15 to 60 days.
- Deciding when to lock depends on your comfort with payment range, closing date certainty, and tolerance for market fluctuations.
- Your locked rate can change if loan details, such as credit score, loan amount, or property value, materially shift.
- Some lenders offer a 'float-down' option allowing for a one-time rate adjustment if market rates significantly improve after locking.
What a Rate Lock Is
A rate lock is a lender commitment to honor a specific interest rate and point structure for a set number of days, as long as your loan closes within that window and nothing material changes in your file.
How Long Locks Last
Common lock periods are 15, 30, 45, and 60 days. Longer locks generally cost more, because the lender is taking on more market risk. For a typical purchase, a 30 or 45 day lock aligns with the contract timeline.
What Can Break a Lock
Your locked rate is tied to the specifics of your file. It can change if:
- Your credit score changes materially
- The loan amount or down payment changes
- The appraised value comes in different than expected
- Occupancy or property type changes
- The loan program changes
- The lock expires before closing
When to Lock
Lock early if you are close to the top of your comfortable payment range, your closing date is firm, or you simply want certainty. Certainty has real value.
Consider floating if your closing is far out, you have payment flexibility, and you understand rates can move against you as easily as for you.
Nobody reliably predicts short-term rate movement. Anyone who tells you otherwise is guessing.
What If Rates Drop After You Lock?
Ask your lender about a float-down option before you lock. Some lock agreements include a one-time float-down if the market improves by a defined margin. Terms vary by lender and program, and the option may carry a cost.
If no float-down is available and the market moves significantly, refinancing later is a separate decision with its own costs to weigh.
What If the Lock Expires?
Extensions are usually available for a fee, often priced per day. If the delay was caused by the lender, ask whether the extension can be covered. Avoiding extensions is one more reason to return documents quickly.
Questions to Ask Before You Lock
- What is the exact lock expiration date?
- What does an extension cost per day?
- Is a float-down available, and what triggers it?
- What would change this rate?
- Can I get the lock confirmation in writing?
Get the Lock Terms in Writing
Every lock should come with a written confirmation showing the rate, points, and expiration. Ask us to walk through your lock options before you decide.
Frequently Asked Questions
What is a mortgage rate lock?
A mortgage rate lock is a lender's guarantee to hold a specific interest rate and points for a set duration, usually 15 to 60 days. This ensures your rate won't change if market rates fluctuate before your loan closes, provided your loan details remain consistent.
When should I lock my mortgage rate?
Consider locking your rate early if you prefer certainty, your closing date is firm, or you're near your comfortable payment limit. If your closing is further out or you're comfortable with potential rate shifts, you might consider floating for a period.
What happens if rates drop after I lock?
If rates drop after you've locked, you might be able to utilize a 'float-down' option if your lender offers one. This feature, which may come with a cost, allows for a one-time rate adjustment if market conditions improve by a defined margin. Terms vary by lender.
Related: See our monthly-updated Mortgage Rates 2026 forecast — what drives rates and whether they may go down this year.