Mortgage Interest Calculator
Total interest paid over the life of a mortgage.
Calculate total interest paid on a mortgage over its full term at a given rate. Enter loan amount and see the result instantly.
What this tool does
Enter loan amount, annual rate, and term. The tool shows total interest, total repayment, and interest-to-principal ratio.
Enter Values
Formula Used
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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.
200,000 at 5% over 25 years costs 150,754 in interest — 75% of the original loan again. Mortgages concentrate huge interest costs over long terms. Shortening the term, paying down faster, or accepting a upper rate for a shorter fix all affect this number materially.
Run it with sensible defaults
Using loan amount of 200,000, annual rate of 5%, term of 25, the calculation works out to 150,754.02. 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 — Loan Amount, Annual Rate, and Term — do not pull with equal force. Not every input has equal weight. Flip one at a time toward extreme values to feel which ones move the needle most for your situation.
How the math works
Total repayment (monthly × months) minus principal gives total interest. The working is transparent — you can verify every step yourself in the formula section below. No black box, no opaque "proprietary model".
Why this matters before you sign
A mortgage is usually the biggest single financial commitment a person makes. The difference between a well-chosen product and a hasty one can run into tens of thousands over the life of the loan. Running the numbers here before committing is the cheapest form of due diligence available.
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.
Mortgage interest total produces a cost figure based on the inputs provided.
Inputs
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 repayment (monthly × months) minus principal gives total interest.
References
Frequently Asked Questions
Why is interest so high?
How does rate change total interest?
Does offsetting reduce interest?
Interest-only vs repayment total interest?
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