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FinToolSuite
Updated April 20, 2026 · Mortgage · Educational use only ·

Mortgage Comparison Calculator

Compare two mortgage offers side by side.

Compare two mortgage offers by total cost across the introductory period, including arrangement fees that can dwarf the monthly difference.

What this tool does

This calculator totals the cost of two mortgage offers over a specified period by combining monthly payments with arrangement fees, then identifies which offer costs less overall. The result shows the total expense for each offer in your currency, making direct comparison straightforward. Monthly payment amount and arrangement fee are the primary drivers of the outcome. A typical use case is evaluating two offers from different lenders over an introductory period—for example, comparing a lower monthly payment with a higher fee against higher monthly payments with a lower or waived fee. The calculation is illustrated for educational purposes and covers only the costs you input; it excludes early repayment charges, exit fees, and variations in rate after the comparison period, which may affect the true long-term cost.


Enter Values

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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. 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 option with the lower calculated total 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.

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

Comparing £1,250 and £1,304 over 24 months shows 704.00 as the more cost-effective mortgage option.

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 Result704.00

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

The calculator computes the total cost for each mortgage offer by multiplying the monthly payment by the number of months in the comparison period, then adding the arrangement fee. It then calculates the absolute difference between the two total costs to show the saving. The model assumes a constant monthly payment throughout the period and treats both offers identically in structure. It does not account for early repayment charges, exit fees, overpayment flexibility, interest rate changes, payment holidays, or variations in payment amounts over time. Users should manually incorporate any additional fees or charges not captured in the monthly payment or arrangement fee fields to ensure a complete comparison.

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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