A loan calculator uses the standard amortisation formula to work out equal monthly repayments over a fixed term. Each payment covers interest accrued on the outstanding balance plus a portion of the principal. In the early months, most of your payment is interest; as the balance falls, more goes towards principal.
The total interest paid depends heavily on the interest rate and term. A £200,000 mortgage at 5.5% over 25 years costs £159,489 in interest. Reducing the term to 20 years saves £34,280 in interest. Making overpayments of even £100 per month can save tens of thousands of pounds and years off the term.
The calculator shows monthly payments, total interest and total repayment. For mortgages specifically, most deals are 2 or 5-year fixed rates that revert to a standard variable rate — use the rate on your current offer rather than an estimated future rate.
Once you know your monthly payment, use the Savings Goal Calculator to model an overpayment fund, or the Pension Calculator to ensure your loan repayments don't crowd out retirement savings.
Tap Calculate — monthly payment, total repaid and total interest
Monthly payment by loan amount (25-year term)
Estimated monthly repayment on a repayment loan over 25 years at 4%, 5.5% and 7% interest. Use the calculator above for any amount, rate or term.
Amount
at 4%
at 5.5%
at 7%
£10,000
£53
£61
£71
£25,000
£132
£154
£177
£100,000
£528
£614
£707
£200,000
£1,056
£1,228
£1,414
£300,000
£1,584
£1,842
£2,120
Frequently Asked Questions
ℹ️ Accuracy note: Illustrative only. Actual rates and terms depend on your lender and credit profile. Consult a regulated financial adviser before taking on debt.
Annual Percentage Rate — the total cost of borrowing per year including interest and mandatory fees. Always compare loans using APR.
No — only standard scheduled repayments. Charges vary by lender.
Yes — enter the mortgage amount, your rate and term for an estimate.
Using the standard amortisation formula: M = P × [r(1+r)ⁿ] ÷ [(1+r)ⁿ−1].
UK personal loan rates in 2025 typically range from 5.9% to 39.9% APR. Rates below 8% APR are competitive. The rate you receive depends heavily on your credit score, income and the loan amount. Always compare the APR — not just the interest rate — as APR includes all mandatory fees.
Paying an extra £100 per month on a £200,000 25-year mortgage at 5.5% saves approximately £23,000 in interest and reduces the term by around 3 years. Most mortgage providers allow overpayments of up to 10% per year without penalty. Check your mortgage terms before making overpayments.
A secured loan is backed by an asset (usually your home), allowing larger amounts and lower rates — but your property can be repossessed if you miss payments. An unsecured personal loan requires no collateral and offers amounts up to £25,000, typically at higher rates. Mortgages are secured loans.