FinToolSuite

Mortgage Comparison Calculator

Updated April 17, 2026 · Mortgage · Educational use only ·

Compare two mortgage offers side by side.

Compare two mortgage offers by total cost including arrangement fees across the introductory period. Enter offer a monthly payment and see the result instantly.

What this tool does

Enter rate, fee, and monthly payment for two offers plus the introductory period. The tool shows total cost and which offer wins.


Enter Values

Formula Used
Monthly payment
Arrangement fee
Comparison period

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Disclaimer

Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.

Headline rate alone is misleading. A 3.5% rate with a 2,000 fee can cost more than a 3.8% rate with no fee over a 2-year fix. The true comparison is monthly payment times period plus the fee. A 0.3% rate difference on 250,000 saves about 54/month — 1,296 over 2 years — which the 2,000 fee eats for breakfast.

Run it with sensible defaults

Using offer a monthly payment of 1,250, offer a arrangement fee of 2,000, offer b monthly payment of 1,304, offer b arrangement fee of 0, the calculation works out to 704.00. Nudge the inputs toward your own situation and the output recalculates instantly. The defaults are meant as a starting point, not a recommendation.

The levers in this calculation

The inputs — Offer A Monthly Payment, Offer A Arrangement Fee, Offer B Monthly Payment, Offer B Arrangement Fee, and Comparison Period — do not pull with equal force. Two inputs usually tip the answer one way or the other. Identify which ones matter most by flipping each value past a round threshold and watching whether the winning option changes.

How the math works

Total cost = (monthly × months) + fee. Compare both offers over the same period. Does not include early repayment charges or exit fees — add them if relevant. The working is transparent — you can verify every step yourself in the formula section below. No black box, no opaque "proprietary model".

What the headline rate hides

Lenders quote a rate; what you pay is a blend of that rate, fees, insurance, and any early-repayment penalty built into the product. The figure here isolates the core interest cost so you can compare like-for-like across deals — then add the other costs separately before signing anything.

What this doesn't capture

The figure excludes arrangement fees, valuation costs, legal fees, insurance, and any early-repayment charges — those can add several thousand to the headline cost. Rate changes at renewal for fixed-term deals will shift the picture further. Use this for the core interest/principal math and add the other costs on top.

Example Scenario

Mortgage comparison produces a winner based on the inputs provided.

Inputs

Offer A Monthly Payment:1,250 £
Offer A Arrangement Fee:2,000 £
Offer B Monthly Payment:1,304 £
Offer B Arrangement Fee:0 £
Comparison Period:24
Expected Result£704.00

This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.

Sources & Methodology

Methodology

Total cost = (monthly × months) + fee. Compare both offers over the same period. Does not include early repayment charges or exit fees — add them if relevant.

Frequently Asked Questions

Why compare over the fix period, not the full term?
Because rate and fee apply only to the fix. After it ends, you will compare again — so the fix is the right window for this decision.
What about reversion rate?
If you are likely to stay on the reversion rate after the fix ends, add those months at that rate. Most borrowers remortgage to a new fix instead.
Do I include product fees in the mortgage?
If the fee is added to the loan, include interest on the fee. Simplest approach: pay the fee upfront and model both offers on the same loan amount.
What if periods differ?
Compare each offer over its own fix period. A 5-year fix and a 2-year fix are two different products; compare per-year cost rather than absolute.

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