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Mortgage Calculators

Mortgage Comparison Calculator

Compare two mortgage scenarios side by side — different rates, terms, down payments, or loan amounts — to see which one actually costs less.

Uses the same standard amortization formula lenders use, applied to both scenarios simultaneously.

AScenario A
$
%
yr
BScenario B
$
%
yr
Scenario A
$2,528/mo
Total interest
$510,178
Total paid
$910,178
Scenario B
$2,398/mo
Total interest
$463,353
Total paid
$863,353
Scenario B costs less
$46,825
Over the life of the loan, Scenario B saves $46,825 in total payments.
Δ Monthly P&I (B − A)
-$130
Δ Total interest (B − A)
-$46,825
Δ Lifetime cost (B − A)
-$46,825
Overview

How the Mortgage Comparison Calculator Works

Most mortgage decisions come down to a comparison — 15-year vs 30-year, 6.5% vs 6.0%, more down vs less down, buy points vs don't. This calculator runs both scenarios through the same amortization math at once so you can see the real dollar difference in monthly payment, total interest, and lifetime cost, without flipping tabs.

Formula

The Math Behind the Calculator

Both scenarios use M = P × r / (1 − (1 + r)^−n) with the inputs you provide. The comparison then reports Δmonthly payment, Δtotal interest, and Δlifetime cost between Scenario A and Scenario B.

Example

A Worked Example

Scenario A: $400,000 loan at 6.50% for 30 years → $2,528/mo, $510,000 total interest. Scenario B: $400,000 at 6.00% for 30 years → $2,398/mo, $463,000 total interest. Scenario B costs $130 less per month and saves about $47,000 over the life of the loan — often more than enough to justify a modest rate-buydown fee.

How to use

How to Use the Mortgage Comparison Calculator

  1. 1Enter the loan amount, rate, and term for Scenario A.
  2. 2Enter the alternative loan amount, rate, and term for Scenario B.
  3. 3Read the delta card at the bottom: it tells you which scenario is cheaper and by how much.
  4. 4Adjust either scenario in real time to test rate-shopping quotes or refinance offers.
Interpretation

What the Results Mean

  • Δ monthly payment is the difference in what leaves your account each month.
  • Δ total interest is the lifetime interest savings (or extra cost) of the cheaper scenario.
  • A negative delta means Scenario B is cheaper; a positive delta means Scenario A is cheaper.
Avoid

Common Mistakes to Avoid

  • Comparing a lower monthly payment on a longer term without noticing the extra interest.
  • Ignoring closing costs and points when comparing rates — a lower rate can cost thousands upfront.
  • Forgetting that a bigger down payment reduces the loan amount, so make sure both scenarios reflect that.
Keep going

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Calculate monthly savings, break-even point, and lifetime interest if you refinance your mortgage.

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Generate a full month-by-month amortization schedule for any mortgage, with the principal/interest split and running balance for every payment.

FAQ

Frequently Asked Questions

Which scenario should I pick?+

The one that fits your cash flow AND has lower total interest, if possible. If one scenario has a lower monthly payment but much higher total interest, that's a trade-off — not a win.

Does this include taxes and insurance?+

No — the comparison focuses on the P&I differences that drive the actual loan cost. Taxes and insurance are usually similar between two scenarios on the same house.

Can I compare 15-year vs 30-year here?+

Yes. Set Scenario A term to 15 and Scenario B term to 30, keep everything else equal, and the delta card shows the true monthly cash-flow vs lifetime-interest trade-off.

Financial Disclaimer

This calculator is for educational and estimation purposes only. It does not provide financial, mortgage, tax, investment, or legal advice. Actual rates, payments, taxes, fees, insurance costs, eligibility, and loan terms vary by lender, location, credit profile, and market conditions. Always compare official offers and consult a qualified professional before making financial decisions.

Last updated June 2026 · Prepared by the mCalculator Editorial Team