Your mortgage rate can move $60 a month in a single week. On a $400,000 loan, that’s the difference between a 6.5% payment and a 6.75% payment, and over 30 years it adds up to roughly $20,000 in extra interest. Which is why the day you lock matters as much as the lender you choose.
Locking in a mortgage rate sounds simple. You pick a rate, the lender freezes it, you close. In practice, locks come with windows, fees, fine print, and a set of rules about what voids them. Get any of that wrong and you can end up paying for protection you never got to use.
What a Rate Lock Actually Guarantees
A lock is a written commitment from the lender. For a set number of days, your interest rate and your points stay exactly where they are, even if the market jumps half a percent the next morning. What it doesn’t freeze is everything else.
Your closing costs can still shift. Escrow figures move if the county’s tax assessment doesn’t match what the seller was paying. And your rate itself can change if your financial profile changes. Switching from a single-family home to a duplex, dropping your down payment below the threshold you were priced at, or taking on new debt can all push you into a different pricing tier.
That last one catches people constantly. Lenders re-pull credit shortly before closing. A financed truck or a new card with a $4,000 balance can drop your score 20 points, and the lock only holds the rate your file was originally priced at. Leave your credit alone between application and closing. No furniture financing, no “just to see” limit increases.
How Long a Lock Do You Need?
Locks come in 15, 30, 45, 60, and 90-day terms, sometimes longer for new construction. The 30-day lock is the default for purchases, yet plenty of deals take 40 to 50 days, especially when an appraisal comes in low and has to be disputed.
Here’s what longer locks typically cost, charged as a rate bump or points:
- 30 days: baseline pricing, no adjustment
- 45 days: about 0.125% higher in rate, or 0.25 points
- 60 days: about 0.25% higher, or 0.5 points
- 90 days or more: 0.375% to 0.5% higher
That 0.25% bump on a $400,000 loan runs close to $60 a month, so you’d be handing over roughly $1,800 in points to avoid a two-week gap. Sometimes that’s cheap insurance. Sometimes it’s money you didn’t need to spend at all. Ask your loan officer for their average days-to-close over the past quarter. A lender closing in 26 days on average doesn’t justify a 60-day lock.
Know Today’s Market Before You Commit
You can’t judge a lock offer without knowing what the going rate is. Pricing varies by loan type, credit tier, down payment, occupancy, and property. A 30-year fixed for a well-qualified borrower and an FHA loan for someone with a 660 score are different products with different baselines. Before you agree to anything, check where 30-year fixed mortgage rates actually sit today, then compare your quote against that instead of against the first number a lender puts in front of you.
It also helps to know that the advertised “lowest” rates are built on assumptions you may not meet: 25% down, a 780 score, no cash-out, owner-occupied. Our reality check on the lowest mortgage rates available today walks through which of those levers you can actually pull. Loan size matters too, and buyers in expensive markets should understand how California mortgage rates get priced on jumbo balances before they lock anything.
Float-Downs, and Whether You Should Pay for One
A float-down lets you grab a lower rate if the market improves during your lock period. Most allow it once, and only if rates drop by a set amount, typically 0.25% or 0.5%. Some are free. Most cost 0.25 to 0.5 points.
If you’re locking on a day when rates just spiked, a float-down is worth pricing. If you’re locking after a rally, with the market already near recent lows, you’re buying insurance against a scenario that only helps you a little.
When to Lock and When to Float
Nobody can call next week’s rate. What you can control is how much risk your budget carries and whether you can absorb a worst-case payment.
Lock sooner when:
- Your closing is inside 30 days and a $75 monthly increase would hurt
- You’re already near the debt-to-income ceiling your lender will approve
- A Fed meeting, CPI report, or jobs number lands before closing and you have no edge on the outcome
- You’ve found a rate you’re happy with and more shopping is unlikely to beat it by enough to matter
Floating can make sense when you’re 60-plus days out, your finances have slack, and you’d genuinely be fine buying the rate down later if things go sideways. Run both paths side by side before deciding. A mortgage rate lock calculator will show you what the protection costs against what floating risks.
How to Get a Better Rate Locked
Shop three lenders on the same afternoon
Rates move throughout the day, so a quote from Tuesday morning and one from Thursday evening aren’t comparable. Pull three Loan Estimates within a few hours and compare the rate next to the APR, origination fee, and lender credits. Two lenders quoting 6.5% can be $3,000 apart across the life of the loan once fees are counted. Our breakdown of conventional mortgage rates and the variables behind them covers what those quote sheets tend to bury.
Use one lender’s offer against another
Loan officers have pricing discretion. A competing written estimate that beats theirs by 0.125% is often enough to get a match, a credit, or a fee waived. Ask directly: “Can you get to 6.375%? I have a written offer at that number.” The worst answer you’ll get is no, and you’ve lost nothing.
Fix the weak spots in your file first
A 20-point credit score difference can move you a full pricing tier. Paying a revolving balance down below 30% utilization, or waiting out a recent late payment, can be worth more than any negotiation. Loan type matters just as much, since VA and USDA pricing, fees, and eligibility rules don’t line up with conventional at all.
Time the lock to your closing date
Lock the moment you have a signed purchase contract and a realistic closing date. Not the day you start shopping, and not three weeks later after watching rates every morning. Those three weeks of watching are exactly how buyers end up locking at the worst point of a short-term swing.
What to Do If Rates Fall After You Lock
First, read your confirmation. If you bought a float-down, use it before the deadline stated in the paperwork, not the day it occurs to you. If you didn’t, ask your loan officer about a one-time re-lock or a pricing exception. On purchases that request rarely succeeds, but it’s free to ask, and a lender with a competitive streak will occasionally eat the difference to keep the deal.
Don’t threaten to switch lenders unless you mean it. Starting over means a new application, a new appraisal, and a new lock at whatever today’s rate happens to be.
Read the Extension Clause Before You Need It
The clause that costs the most money is the one nobody reads: what happens if you close after the lock expires. Some lenders offer a short extension for a flat fee, say 0.125% of the loan amount for 10 days. Others let the lock die and reprice you at the market, which is a brutal surprise if rates climbed while you waited on a slow appraiser.
Ask two questions when you lock. How much is a 15-day extension, and who pays for it if the delay is the lender’s fault? Get both answers in the same email as your lock confirmation. Delays caused by the lender’s own underwriting or appraisal scheduling shouldn’t land on your side of the ledger, and a loan officer who agrees to that in writing is one worth keeping.