Total Mortgage Repayment Calculator
Over a 25-year term, you'll pay back significantly more than you borrowed. On a typical £250,000 mortgage at 5%, total interest adds up to around £187,000 – 75% of the original loan.
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Many buyers focus only on monthly payments without considering total cost. A 1% rate difference can mean tens of thousands in extra interest. A 30-year term has lower payments but costs substantially more overall.
Understanding the true cost helps you make better decisions about term length and overpayments. Enter your details below to see exactly how much you'll pay.
Mortgage Details
Arrangement fees, valuation costs, etc.
Total Cost Breakdown
Monthly Payment
£0
Total Repaid Over 25 Years
£0
Capital Borrowed
£0
Total Interest
£0
Interest as % of Total Cost
0%
For every £1 borrowed, you pay £0.00 back
Rate Impact (±0.5%)
At 4.0%
£0
At 5.0%
£0
A 1% rate difference = £0 over the term
vs Interest-Only
Interest-only would cost £0/month but £0 more overall
What this total really represents
The "total cost" combines your capital repaid (the amount you borrowed) and the interest charged across every year of the term. On most 25-year mortgages, total interest is 60–90% of the original loan — meaning you genuinely pay back close to twice what you borrowed at 5%+ rates.
Two levers move this number most: the term length (a 30-year term costs 30–40% more in interest than a 25-year one) and the rate at each remortgage. Even small overpayments early in the term — when interest dominates the payment — can shave years off and save tens of thousands.
Understanding Total Mortgage Cost
Most people focus on the monthly payment when choosing a mortgage, but the total repayment amount tells the real story. Understanding this helps you make better decisions about rates, terms, and overpayments.
Why Total Cost Matters More Than Monthly Payment
The Monthly Payment Trap
A 30-year term has lower monthly payments than a 25-year term, but you could pay £50,000+ more in total interest. Lenders advertise monthly payments because they look more affordable—but you're paying more overall.
Real Example
£250,000 at 4.5%:
• 25 years: £1,390/mo, £417k total
• 30 years: £1,267/mo, £456k total
Difference: £39,000 extra
How Small Rate Changes Affect Lifetime Cost
Interest rate differences that seem trivial have enormous long-term impact:
4.0%
£395,000 total
on £250k/25yr
4.5%
£417,000 total
+£22,000
5.0%
£439,000 total
+£44,000
A 1% rate difference = approximately £44,000 over 25 years. This is why mortgage rate shopping and timing can save—or cost—you a small fortune.
Repayment vs Interest-Only: The True Difference
Repayment Mortgage
- • Each payment reduces your debt
- • Mortgage fully paid at end of term
- • Higher monthly payments
- • Less total interest paid
- • You own the property outright
Interest-Only Mortgage
- • Only pay interest each month
- • Full debt remains at end of term
- • Lower monthly payments
- • Much more total interest paid
- • Need repayment plan for capital
Warning: Interest-only mortgages look cheaper monthly but cost significantly more overall, AND you still owe the full amount at the end. They're typically only suitable for buy-to-let investors or those with a solid repayment strategy.
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