A rate lock guarantees your interest rate and points for a set period, usually 30 to 60 days, while your loan closes. Most buyers lock once they’re under contract. Longer locks can cost more, extending an expiring lock usually costs a fee, and a float-down option lets you take a lower rate if rates fall, sometimes for a fee.
How locks work
- The lock covers a specific rate, points, loan amount, loan type and closing date.
- If key details change, such as your credit score, loan amount or down payment, pricing can change even while locked.
- If closing slips past the lock’s expiration, you’ll need an extension or a relock at current rates.
When to lock
Most lenders let you lock once you have a signed contract and an application. Locking early protects you from rising rates but means a longer, sometimes costlier lock. Floating saves the cost and lets you benefit if rates fall, but exposes you to increases. How much is at stake?
Try it: Rate sensitivitySee how your payment and buying power change if rates move a quarter or half point before you lock.Lock periods and costs
| Lock length | Typical use |
|---|---|
| 15 to 30 days | Quick closings, refinances |
| 45 days | Most purchases |
| 60 to 90 days | Slower closings, some FHA and VA loans |
| Longer | New construction, usually for a fee |
Float-downs
A float-down option lets you reduce your locked rate if market rates fall by a set amount before closing. Some lenders include one; others charge for it. Ask how much rates must drop and whether there’s a fee.
Protect your lock
- Schedule inspections and the appraisal quickly.
- Respond to underwriting the same day.
- Ask your lender the cost of an extension before you need one.
Compare lock terms along with rates when you shop; see how to shop for a mortgage and compare mortgage offers.
Common questions
When should I lock my mortgage rate?
Most buyers lock once they have a signed purchase contract and have applied with a lender.
What happens if my rate lock expires?
You’ll need an extension, usually for a fee, or a relock at current rates.
What is a float-down?
An option to lower your locked rate if market rates fall by a set amount before closing, sometimes for a fee.
Updated October 2026. Educational content. OfferBacked is not currently a lender and doesn’t issue pre-approvals or loans.