When Should You Lock Your Mortgage Rate?

Once you have an accepted offer, one question starts nagging at almost every buyer: should I lock my mortgage rate now, or wait and hope rates dip before closing? You can't outguess the bond market — but you can make a smart, unemotional decision about when to lock.

Rates move every day, for reasons that have nothing to do with you — inflation reports, Fed commentary, jobs numbers. I've watched buyers win and lose the waiting game in the same week. The ones who come out ahead aren't the ones who timed the market. They're the ones who locked when the payment worked and stopped watching the news.

What is a mortgage rate lock, exactly?

A rate lock is your lender's written commitment to hold a specific rate and price for a set window — usually 30, 45, or 60 days — while your loan gets underwritten and closed. If rates jump the day after you lock, you're protected. Your rate doesn't change because the market did.

A lock isn't loan approval, and it isn't a guarantee that any rate will be available before you lock. It's a shield for the rate you were quoted on the day you locked. Until you lock, you're floating, and a quoted rate can change by the afternoon.

When can you lock — and when should you?

Most buyers lock shortly after they have an accepted offer and a closing date, because the lock period has to cover you through closing. So the practical question isn't "can I lock?" — it's "should I lock today or float?"

My advice is boringly consistent: if the payment at today's rate fits your budget, lock it. Floating to chase a lower rate is a bet with lopsided stakes. If rates fall a little, you save a little. If they spike, your payment — and sometimes your qualification itself — is at risk. A buyer stretching to qualify can lose the house to a half-point move.

What does a quarter point actually cost?

Let's put real dollars on it, using illustration numbers — not a quote. Say you're borrowing $300,000 on a 30-year fixed loan and you're deciding whether to lock at 6.5% or float. While you wait, the market moves an eighth here, an eighth there, and you end up at 6.75%.

• At 6.5%, principal and interest run about $1,896 a month.
• At 6.75%, the same loan runs about $1,946 a month.

That quarter point costs roughly $50 a month — about $18,000 over 30 years if you kept the loan the full term. Now flip it: if rates had fallen a quarter instead, you'd have saved the same amount. The math is symmetric. What isn't symmetric is your situation — you have a closing date, a budget, and a house you don't want to lose. That's why "lock when the payment works" beats "wait and see."

What happens if your lock expires before closing?

Closings slip — appraisals run long, sellers need extra days, paperwork stalls. If your lock runs out first, you can usually extend it for a fee, often somewhere around 0.125% to 0.375% of the loan amount depending on how long you need. On that $300,000 loan, a 0.25% extension fee is $750 — real money for a delay you didn't cause. If the delay is the lender's fault, many lenders will eat the extension cost; it never hurts to ask.

The cheaper move is to get the lock period right up front. If your closing is 40 days out, a 30-day lock is wishful thinking — take the 45. A slightly longer lock typically costs a hair more, but it's cheap insurance compared to an extension under deadline pressure.

The bottom line

Rate locks exist to take one variable off your plate during the most stressful weeks of buying a home. Lock when the payment works for your budget, match the lock period to your real closing date with room to spare, and ask about float-down terms before you commit. If you want to understand the forces moving rates in the first place, read my post on how mortgage rates are actually determined — it'll cure you of trying to outguess them.