Mortgage Rate Difference Calculator

Hold balance and term constant to isolate how a rate change affects monthly P&I, interest, remaining balance, rate-linked cost break-even, and a full basis-point sensitivity ladder.

Rate sensitivity workspace

See what every basis point changes

Hold balance and term constant, compare two fixed rates, inspect 5-year or custom-horizon cost, test rate-related upfront costs, and reverse-solve a target payment.

Same loan, two rates

Isolate the rate difference

Loan amountTerm yearsExtra monthsDisplay currency

Rate AFixed annual rate (%)Rate-related upfront cost (optional)

Rate BFixed annual rate (%)Rate-related upfront cost (optional)

Comparison horizon (years)

Why this mattersCompare the time you may actually keep the loan

The optional upfront fields are for rate-linked points/credits or another rate-specific price difference you want to test. They are not an APR classification engine; use the Mortgage APR Calculator for that.

Reverse solve

What rate fits a target monthly P&I?

Target monthly principal & interest

——

A/B detail

Payment, interest, equity and rate-linked cost

Rate A

Monthly P&I: —
Lifetime interest: —
Horizon interest: —
Principal paid by horizon: —
Balance at horizon: —
Interest + entered upfront cost: —

Rate B

Monthly P&I: —
Lifetime interest: —
Horizon interest: —
Principal paid by horizon: —
Balance at horizon: —
Interest + entered upfront cost: —

Basis-point ladder

Stress-test Rate A from −100 to +100 bp

Shift	Rate	Monthly P&I	Δ vs Rate A	Horizon interest	Lifetime interest	Horizon balance

Cumulative comparison

Watch interest and balance differences evolve

Elapsed	A cumulative interest	B cumulative interest	B − A interest	A balance	B balance	B − A balance

Method & scope

Fixed-rate principal-and-interest comparison

Both scenarios use the same entered principal and amortization term so the rate effect is isolated.
Monthly P&I uses standard fixed-rate amortization with annual rate ÷ 12.
The horizon cost comparison uses cumulative modeled interest plus only the rate-related upfront amounts you enter.
The basis-point ladder changes Rate A only; it does not model a lender quote or eligibility.

APR can include points, broker fees and other charges; note rate alone is not total loan cost.
Taxes, homeowners insurance, mortgage insurance, HOA and escrow are intentionally excluded.
Compare Loan Estimates on the same loan type and timeframe before choosing an offer.
This is a planning estimate, not lending, tax, legal or financial advice.

Core borrowing, saving & investing workflows

Start with the broad calculator that matches the decision, then move to a specialist only when the loan structure, cash flow, tax treatment, debt strategy or savings goal genuinely changes.

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Compare rates on equal footing

Use the same balance and amortization term for both rates so the result isolates the rate effect. CFPB guidance recommends comparing the same kind of loan and reviewing monthly principal and interest, upfront lender costs, credits, and the time you expect to keep the loan.

Why the five-year or custom horizon matters

A lifetime-interest number can be useful, but many borrowers sell or refinance earlier. The horizon view shows cumulative interest, principal paid, and remaining balance at the time you actually want to compare.

Points and credits can change the answer

If one rate requires more points or receives a lender credit, enter only that rate-linked upfront difference here to see when modeled interest savings recover it. For formal APR treatment and broader finance charges, use the Mortgage APR Calculator.