Mortgage Rate Lock vs Float — Which Should You Choose Before Closing?

Direct Answer

Last verified on: June 28, 2026

Editorial note: Rate locks are agreements between a borrower and a lender. Lock periods and float-down rules vary by institution. This guide assumes a standard 30-year fixed-rate mortgage. Always review your Loan Estimate for specific lock terms.

Research method: Daily Calcs reviewed CFPB (Consumer Financial Protection Bureau) guidance on mortgage rate locks, Freddie Mac PMMS (Primary Mortgage Market Survey) volatility data, and typical lender lock-fee structures. All sources verified on June 21, 2026.

Rate Lock vs. Float: The Trade-Off

Choosing between locking and floating is a balance of risk versus potential reward.

When to Lock Your Rate

1. You have a signed purchase agreement

Once you have a contract on a house, the clock starts ticking toward closing. If you float and rates jump 0.5% in the final two weeks, your monthly payment could increase by $150-$250. Locking removes this risk.

2. The rate is already at or below your target

If your budget requires a 6.5% rate and the lender offers you 6.3%, lock it immediately. Gambling for 6.0% isn’t worth the risk of ending up at 6.8%.

3. You have a long closing window

If your closing is 60 days away (due to a contingent sale or new construction), the risk of market movement is higher. A long-term lock protects you from a month of volatility.

When to Float Your Rate

1. Rates are in a steep downward trend

If every weekly report from the Freddie Mac PMMS (Primary Mortgage Market Survey) shows rates dropping, floating may save you money. However, this is a gamble.

2. You are closing very quickly

If you are closing in 7-10 days, the window for a significant rate move is small. The cost or risk of locking may be unnecessary.

3. You have a “Float-Down” option

A float-down allows you to lock your rate for safety but “float down” to a lower rate if the market drops by a certain percentage (e.g., 0.25%). This is the “best of both worlds” strategy.

The Cost of Locking: Points and Fees

Some lenders offer different lock terms based on what you pay:

• No-Cost Lock: The lender locks the rate as part of the application, but the rate may be slightly higher.
• Paid Lock: You pay an upfront fee to secure a lower rate for a longer period.
• Discount Points: You pay an upfront fee (1 point = 1% of loan amount) to permanently lower the APR (annual percentage rate). This is different from a lock; it’s a price paid for a lower lifetime rate.

How a 0.25% Shift Affects You

To understand why the lock decision matters, look at the impact on a $300,000 loan at 6.5%:

A “bad” float increases your monthly cost by $42 and your lifetime cost by $15,440.

Lock vs Float Decision Checklist

• Lock once you have a signed purchase contract and a rate that fits your budget
• Float only if rates are clearly trending down AND you can absorb a 0.25%+ increase
• Ask about float-down option: cost, minimum rate drop trigger, and expiration
• Match lock period to closing timeline — add 7-10 days buffer for delays
• Run ±0.25% scenarios in the Mortgage Calculator
• Never float without understanding dollar impact — $42/month × 360 months adds up
• For refinances, confirm break-even before locking — see Refinance Calculator
• Request lock extension before expiration if closing slips — extensions cost 0.125-0.25% typically

Assumptions and Limitations

Payment examples use $300,000 at 6.5% over 30 years. Lock fees, float-down costs, and extension charges vary by lender and are not included in payment comparisons.

Rate direction is unpredictable — Freddie Mac PMMS shows weekly averages, not forward guidance. This guide compares lock vs float tradeoffs — not market forecasts.

Calculator Methodology

The rate impact calculations use:

• loan amount: $300,000
• term: 30 years
• base rate: 6.5%
• monthly compounding using the standard amortization formula.

Standard amortization formula:

Payment = P * r(1 + r)^n / ((1 + r)^n - 1)

Official and Supporting Sources

• CFPB (Consumer Financial Protection Bureau): Mortgage Rate Locks
• Freddie Mac PMMS (Primary Mortgage Market Survey)
• Daily Calcs Mortgage Calculator
• How Mortgage Rates Affect Your Monthly Payment
• Closing Costs Explained — what to expect in 2026

Next Step

Check the current average rates on the Freddie Mac PMMS. Then, use the Mortgage Calculator to see exactly how a 0.25% rate increase or decrease changes your monthly payment and total interest.