Mortgage rate lock strategy: when to lock, how long to lock, and what happens if rates move
A rate lock protects you from rising rates during the mortgage process — but lock too early and you pay a premium, lock too short and you risk a costly extension. This guide covers rate lock mechanics, float-down options, lock period pricing, and the decision framework for volatile rate environments.
Locking a mortgage rate at the wrong time — too early, too short, or without a float-down when rates are falling — is an expensive mistake. In a volatile rate environment, the decision of when and how to lock is nearly as important as choosing your lender.
How rate locks work
Lenders quote a rate but it isn't locked — it floats with market conditions until you formally lock.
Most lenders allow locking once you're under contract. Lock period starts on lock date, not application date.
30, 45, 60, 90 days — longer periods cost more. Float-down provisions can be added for a fee.
If market rates rise, you pay your locked rate. If rates fall, you're locked in unless you have a float-down.
Rate lock period pricing
| Lock period | Typical rate premium | Cost on $400k loan (monthly) | Best use |
|---|---|---|---|
| 30 days | Base rate (0 premium) | $0 | Resale closing <30 days away |
| 45 days | +0.125% | +$30/mo | Standard purchase with buffer |
| 60 days | +0.25% | +$60/mo | Complex underwriting or slow market |
| 90 days | +0.375% | +$90/mo | New construction (short build) |
| 120–180 days | +0.5–1.0% | +$120–$240/mo | Pre-construction condos |
Premiums vary by lender and market conditions. Check Freddie Mac's PMMS for current rate trends before choosing lock duration.
The rate lock decision framework
- Rates are rising or volatile
- You close in 30–45 days
- Your budget is tight — rate increase would disqualify you
- You've seen a rate you can afford and want certainty
- Fed meetings or economic data releases are upcoming
- Rates are clearly trending down
- You have more than 30 days before closing
- You can qualify at current rates — rise won't disqualify you
- You have or can add a float-down provision
- Your lender confirms floating is permitted without fee
Float-down provisions: how they work
A float-down provision lets you take a lower rate if market rates drop after you lock, typically subject to a minimum threshold (e.g., rates must drop by at least 0.25%). Cost varies: some lenders include them free; others charge 0.1–0.5% of the loan. A float-down is valuable when you need the certainty of a lock but want downside protection. Ask your lender specifically:
- What is the minimum rate drop required to trigger the float-down?
- Can it be exercised only once?
- Does it reset the lock period or keep the original expiration?
- Is there a fee, or is it included?
The CFPB's rate lock guide lists the key questions to ask any lender before you commit to a lock.
External references
- CFPB — What is a mortgage rate lock?
- CFPB — Comparing loan offers before locking
- Freddie Mac — Primary Mortgage Market Survey (weekly rates)
- Bankrate — Rate lock costs and float-down options
- CFPB — Closing stage and rate lock extensions
- Investopedia — Rate lock definition and mechanics
Common questions
What is a mortgage rate lock?
A rate lock is a lender's commitment to hold a specific interest rate for you for a defined period (typically 30–60 days) while your loan processes through underwriting. If market rates rise during that period, your locked rate is protected. If rates fall, you're locked in at the higher rate (unless you have a float-down provision). The CFPB's rate lock guide explains exactly what the lock covers and what it doesn't.
When should I lock my mortgage rate?
The optimal lock timing depends on rate direction and your closing timeline. In a rising rate environment: lock as early as your purchase contract allows, even if it costs a small premium for a longer lock. In a falling rate environment: consider floating (delaying the lock) or paying for a float-down provision. Most lenders allow you to lock once you have an accepted purchase offer. Freddie Mac's weekly PMMS survey publishes the 30-year average weekly, giving you a data point on the rate trend before deciding to lock.
What does a longer rate lock cost?
Rate lock pricing typically works in 15-day increments above a base 30-day lock. A 45-day lock adds about 0.125–0.25% to your rate; a 60-day lock adds 0.25–0.375%; a 90-day lock adds 0.375–0.5%; some lenders charge 0.5–1.0% upfront for 120-day extended locks on new construction. On a $400,000 loan, a 0.25% rate increase from a longer lock costs roughly $60/month permanently — compare this to the risk of floating and paying an extension fee if closing is delayed. Bankrate's rate lock explainer covers typical pricing by lock duration.
What happens if rates drop after I lock?
Without a float-down provision, you cannot reduce your locked rate if market rates fall — you are bound to your agreed rate. Options: (1) Ask if your lender offers a one-time float-down at no cost for a specified rate drop threshold; (2) Pay for a float-down provision upfront (typically 0.1–0.25% of loan); (3) Let the lock expire and re-lock at the lower rate, accepting the delay risk. The CFPB's lock guide explains your rights and what to ask your lender if rates move significantly after locking.
What is a rate lock extension and what does it cost?
If your closing is delayed beyond your lock expiration, you have two options: (1) Re-lock at current market rates (which may be higher); (2) Pay a lock extension fee, typically 0.15–0.30% of the loan amount per 15-day extension, or a flat $300–$1,500. Who pays depends on what caused the delay — if the lender caused it (appraisal delay, underwriting backlog), they may absorb the extension cost. If the buyer or seller caused it, the buyer typically pays. CFPB's closing stage guide covers timeline management and what to document if a lender-caused delay forces an extension.
Can you switch lenders after locking?
Yes, but you forfeit your lock and any lock fee paid. Switching lenders after a rate lock is costly in two ways: you lose any upfront fee, and you must re-apply and re-lock (at current rates, which may be higher). Switching is worth it if the new lender's rate is significantly better AND you have enough time to process without rushing. If you're close to closing, switching lenders risks losing your rate lock and potentially delaying closing past the contract date. CFPB's loan offer comparison guide walks through how to evaluate competing lender offers before committing to a lock.
Check current rates on the mortgage calculator — or read the rate lock glossary entry.