Direct Answer
Lock your mortgage rate once you have an accepted offer and a stable underwriting file — typically 30 to 60 days before closing. Float only if you can accept the risk of rates rising. Float-down options let you capture a lower rate later but cost an upfront fee or worse initial pricing. If your lock expires, expect an extension fee of about 0.125% to 0.25% of the loan or a flat charge.
Last verified on: June 28, 2026
Editorial note: Rate lock terms vary by lender. This guide covers general timing principles — confirm lock length, extension fees, and float-down rules on your Loan Estimate.
Research method: Consumer Financial Protection Bureau (CFPB) rate lock guidance and Freddie Mac Primary Mortgage Market Survey (PMMS) data reviewed June 28, 2026.
What a rate lock actually does
A rate lock is a lender’s commitment to honor a specific interest rate (and points) for a set number of days while your loan is processed. It protects you from rate increases between application and closing. In exchange, you commit to that rate even if the market improves, unless you pay for a float-down. Locks are quoted in days — 30, 45, or 60 are most common — and longer windows cost more because the lender absorbs more interest-rate risk.
Lock vs float: how to decide
| Situation | Better choice | Why |
|---|---|---|
| Rates trending up | Lock | Protects against further increases |
| Closing within 30 days | Lock | Little time for a favorable move |
| Rates clearly falling and long timeline | Float (cautiously) | Chance to lock lower later |
| Large loan, falling market | Float-down option | Small drop saves meaningful money |
Floating means leaving your rate unlocked in the hope it improves. It is a bet, and the downside (a higher payment for the life of the loan) is usually larger than the upside of a small short-term dip.
Worked example: why timing matters less than you think
On a $400,000 loan, the difference between 6.50% and 6.75% is about $65 per month in principal and interest. Chasing a 0.125% improvement by floating risks the rate moving the other way and locking in a higher payment for 30 years. Use the Mortgage Calculator to see how a small rate change affects your payment, and the Refinance Calculator to confirm a refinance lock clears your break-even.
Worked Example: $350,000 Purchase Closing in 45 Days
Profile: Buyer under contract, closing date 45 days out, current offered rate 6.625%, deciding between 45-day lock and floating.
| Decision | Rate locked | Monthly P&I | 45-day risk | Extension cost if delayed |
|---|---|---|---|---|
| Lock 45 days now | 6.625% | $2,242 | None — rate protected | ~$440-$875 (0.125-0.25% of loan) |
| Float 45 days | Unknown | Unknown | +0.25% = +$57/mo forever | N/A — re-lock at market rate |
| Float-down add-on | 6.625% floor | $2,242 | Protected unless rates drop 0.25%+ | Float-down fee ~$500-$1,000 |
If rates rise 0.25% during float, lifetime interest increases roughly $18,000 on this loan — far more than any float-down fee.
How to Interpret Lock Period Options
| Lock length | Best for | Typical cost premium | Risk if closing delays |
|---|---|---|---|
| 30 days | Quick closings, refinances | Lowest or free | High — expires fast |
| 45 days | Standard purchase timeline | Moderate | Medium |
| 60 days | New construction, contingent sale | Highest | Low — more buffer |
Ask your loan officer: “What is the rate difference between 30, 45, and 60-day locks?” The premium for a longer lock is often cheaper than a last-minute extension.
Assumptions and Limitations
Examples use a $350,000 loan at 6.625% over 30 years. Lock fees, float-down costs, and extension charges vary by lender and loan type. Federal Housing Administration (FHA), U.S. Department of Veterans Affairs (VA), and jumbo loans may have different lock policies.
Rate direction is unpredictable — Freddie Mac PMMS shows weekly averages, not forward guidance. This guide supports timing decisions — not market forecasts.
Avoiding extension fees
- Match the lock length to your realistic closing date plus a buffer.
- Submit documents quickly so underwriting does not stall.
- Tell your lender early if closing is slipping — a planned extension beats a forced re-lock.
Rate Lock Decision Checklist
- Confirm you have an accepted purchase offer before locking (purchase) or complete application (refinance)
- Match lock period to realistic closing timeline plus 7-10 day buffer
- Compare cost of 30-day vs 45-day vs 60-day locks with your loan officer
- Ask about float-down option cost and minimum rate drop threshold
- Run payment impact at ±0.25% in the Mortgage Calculator
- Submit all documents within 48 hours of request to avoid underwriting delays
- Set calendar reminder for lock expiration date minus 5 business days
- If closing slips, request extension before lock expires — not after
Assumptions and Limitations
Payment examples use a $400,000 loan at 6.50% over 30 years. Actual rate impact scales with loan amount — a $200,000 loan sees roughly half the dollar impact per 0.125% rate change.
Lock policies vary by lender and loan type. FHA, VA, and jumbo loans may have different lock terms. Float-down options are not available from all lenders. This guide supports timing decisions — not rate predictions.
Related Reading
- Mortgage Rate Locks vs Floats — a deeper comparison
- When Will Mortgage Rates Go Down? 2026 Outlook — what drives the market
- How Mortgage Rates Affect Your Monthly Payment — the cost of each rate change
Official and supporting sources
- CFPB — When you lock your interest rate, you are protected
- Freddie Mac — Primary Mortgage Market Survey
Next Step
Once you have an accepted offer, ask your loan officer for lock options at 30, 45, and 60 days — then use the Refinance Calculator or Mortgage Calculator to see how each rate point affects your monthly payment before you lock.
Frequently Asked Questions
When should I lock my mortgage rate?
Lock once you have an accepted purchase offer and a stable underwriting file, which usually means 30 to 60 days before your expected closing date. Locking guarantees your interest rate against market increases during processing. The trade-off is that if rates fall after you lock, you do not automatically benefit unless you bought a float-down option. Because predicting short-term rate moves is unreliable, most buyers lock as soon as they are confident the deal will close on schedule rather than trying to time the market for a fraction of a percent.
What is a float-down option and is it worth it?
A float-down option lets you capture a lower rate if the market improves before closing, even after you have locked. Lenders typically charge for it, either as an upfront fee or as slightly worse initial pricing, and they usually require rates to drop by a minimum threshold before the option triggers. It can be worthwhile in a clearly falling-rate environment or on a large loan where a small rate drop saves meaningful money, but on a short lock period the fee often outweighs the expected benefit.
How long should my rate lock be?
Common lock periods are 30, 45, and 60 days, and longer locks cost more because the lender carries the rate risk for a longer window. Match the lock length to your realistic closing timeline plus a small buffer for appraisal and underwriting delays. A lock that is too short risks expiring before closing and forcing a costly extension, while an unnecessarily long lock means paying a premium in rate or points for time you do not need. Ask your loan officer for the average closing time on your loan type.
When do I lock a rate on a refinance?
For a refinance, lock once your application is complete and the appraisal has been ordered, since there is no purchase contract driving the timeline. Refinances often process faster than purchases, so a 30 to 45 day lock is frequently sufficient. Before locking, run the numbers in a refinance calculator to confirm the new rate clears your break-even point after closing costs. Locking a rate that does not actually save you money over your expected time in the home defeats the purpose of refinancing.
What happens if my rate lock expires before closing?
If your lock expires before closing, you generally must either pay an extension fee or re-lock at the current market rate, whichever your lender offers. Extension fees commonly run about 0.125% to 0.25% of the loan amount or a flat charge, and they increase with the length of the extension. To avoid this, communicate early with your lender if your closing is slipping, since a proactive short extension is usually cheaper than a forced re-lock at a higher market rate after the lock has lapsed.
Related guides
- Mortgage Rate Lock vs Float - Guide (2026) Should you lock your mortgage rate now or float and hope for a drop? Learn the risks, rewards, and how a float-down option works in 2026. Free buyer guide.
- Buying Down Mortgage Rate - When It Pays (2026) Learn when buying down a mortgage rate with points pays off in 2026. See break-even math on a $350k loan. Free mortgage points calculator.
- HELOC vs Cash-Out Refinance - Which Wins? (2026) Compare HELOC vs cash-out refinance in 2026: rates, closing costs, and $50k equity draw examples. See which saves more. Free refinance calculator.
- Jumbo Mortgage Rates Guide (2026) 2026 jumbo loan guide: the conforming limit, rate premiums, down payment rules, and payment examples. Free jumbo mortgage calculator.
- Mortgage Rates and Monthly Payment - Guide (2026) See how a 1% rate change adds or subtracts $175 per month on a $300,000 loan. Rate scenarios from 4.5% to 7.5% for every $100k borrowed. Free calculator.