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Rate Lock vs. Float Calculator — What a Rate Move Would Do to Your Payment

Enter a possible rate move between now and closing and see both the downside if rates rise and the upside if they fall. This tool does not predict which way rates will go.

Quick answer: See what happens to your payment if mortgage rates move before you close — in either direction. Not a rate forecast. Enter Loan Amount, Rate You Can Lock Today, Loan Term (years), and Possible Rate Move Before Closing to personalize the estimate. It returns Payment If You Lock Today, Rate If It Rises, and Rate If It Falls so you can compare the impact before choosing a next step. Use it to compare payment, equity, rate, and timing tradeoffs before applying or changing a loan.

SWReviewed by SwitchWize Research Desk · Last reviewed August 19, 2026
Payment If You Lock Today
$2,458
Payment If You Lock Today
$2,458
Rate If It Rises
6.48%
Rate If It Falls
5.98%
Payment If Rates Rise
$2,523
Payment under each scenario
Payment If Rates Fall
$2,393
Monthly Downside If You Float and Rates Rise
$65
Monthly Upside If You Float and Rates Fall
$65
Lifetime Downside If Rates Rise
$23,524
Lifetime Upside If Rates Fall
$23,258
Diagnostic

Locking removes both the $23,259 upside and the $23,524 downside from this rate move.

This tool does not predict which way rates will move — it only shows what a move of the size you entered would do to your payment.

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What to do next

Compare Mortgage Rates

Your action plan
  1. 1

    Compare the leading option against your current setup

    See what happens to your payment if mortgage rates move before you close — in either direction. Not a rate forecast.

  2. 2

    Compare the result against current market-rate options

    Assumptions change the answer, especially when rates, taxes, or timing matter.

  3. 3

    Save the result to Money Map or use the linked next action

    Turn the result into a prioritized action instead of treating it as a one-off number.

Compare Mortgage Rates

This is an educational estimate, not tax, legal, investment, or lending advice. Tax rules, rates, and eligibility change and depend on your full situation. Confirm with a qualified professional or the provider before acting.

Calculator action path

Turn this result into a decision

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About mortgage rates

Mortgage rates depend on loan type (30-yr fixed, 15-yr fixed, ARM, FHA, VA, jumbo), your credit score, down payment, points paid, loan amount, property state, and whether you're purchasing or refinancing. The calculator above uses a representative market rate for payment estimates — your actual rate will vary.

For a personalized rate comparison, use the tool below to see lenders ranked by APR, loan type, and your profile.

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30-yr fixed · 15-yr fixed · FHA · VA · ARM — ranked by APR
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Mortgage rates shown on SwitchWize compare pages include loan type, assumed FICO, LTV, and points. Representative only — verify all terms directly with the lender. Advertising disclosure

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Frequently Asked Questions

Everything you need to know.

Should I lock my mortgage rate now or float it?
This calculator deliberately does not answer that — no one can reliably predict short-term rate moves. What it shows is the size of the risk: enter how much rates could realistically move before your closing date, and see both the extra cost if they rise and the savings if they fall, so you can decide how much uncertainty you want to carry.
How long does a mortgage rate lock last?
Typical lock periods run 30, 45, or 60 days, with longer locks usually carrying a higher fee or slightly higher rate. Confirm your specific lock period and any extension cost with your lender before relying on it through closing.
What is a float-down option?
Some lenders let you lock a rate but still take advantage of a rate drop before closing, usually for an added fee. It removes the pure downside risk of locking while keeping some of the upside of floating — ask your lender whether this is available and what it costs.
Is the Rate Lock vs. Float Calculator — What a Rate Move Would Do to Your Payment free to use?
Yes. SwitchWize calculators are free, and you do not need an account to run scenarios or view the result.
Does using the Rate Lock vs. Float Calculator — What a Rate Move Would Do to Your Payment affect my credit score?
No. Using a calculator does not trigger a credit check. A credit impact can occur only if you apply directly with a lender, card issuer, or provider.
Are the results personalized financial advice?
No. Calculator outputs are educational estimates based on the inputs you enter. Review assumptions and confirm terms directly with providers before making a financial decision.
What should I do after seeing the result?
Use the recommendation module on this page to compare mortgage rates, or run Money Map to compare this home & mortgage decision with your other opportunities.
How does SwitchWize choose related offers?
Related offers are matched by the calculator surface (mortgage) and ranked using SwitchWize data such as rate, fees, trust signals, product fit, and switching friction. Paid relationships do not change organic ranking order.
How fresh are the rates and offers shown?
Rate and offer data is reviewed on a recurring cadence and every offer module shows review context or links to the methodology and disclosure pages.
Where can I see the ranking methodology?
The SwitchWize methodology page explains how rate freshness, editorial review, affiliate disclosure, and category ranking factors work.
Can Money Map use this result?
Yes. Money Map is the broader diagnostic path: it compares savings, mortgage, cards, and debt so you can see whether this calculator result is your highest-impact next move.

Why This Matters

Deciding whether to lock a rate today or float it until closer to closing is really a question about how much payment risk you are willing to carry. This calculator does not forecast rates — it shows the symmetric range of outcomes for whatever size move you enter, so you can decide how much uncertainty you are comfortable holding.

How to Use It

  1. 1Enter your loan amount and the rate you could lock today
  2. 2Enter a possible rate move before closing (try 0.125%–0.5% for a typical window)
  3. 3Compare the payment if rates rise against the payment if they fall
  4. 4Weigh the lifetime downside against the lifetime upside before deciding
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