See exactly where every pound of your loan repayments goes — how much reduces your actual debt versus how much goes to the lender as interest — month by month, year by year.
Results update instantly as you move the sliders. The crossover point, year-by-year table and monthly split chart all recalculate in real time.
| Year | Interest Paid | Principal Paid | Total Paid | Balance Left | % Paid Off |
|---|---|---|---|---|---|
| Adjust sliders to see the breakdown | |||||
Each bar shows one sampled month. Green = principal reducing your debt. Red = interest going to the lender. Watch the green grow and the red shrink.
Every pound you pay toward a loan is split between two things: interest charged by the lender, and principal — the actual debt you borrowed. In the early months of any loan, the split is heavily weighted toward interest. This tool shows you exactly where each payment goes and reveals the precise month when that balance tips in your favour.
Interest on a personal loan is calculated monthly on the outstanding balance. In month one of a £15,000 loan at 7.9% APR, the interest charge is £98.75 (the full £15,000 × 7.9% ÷ 12). Your total monthly payment might be £364. So only £265 of that first payment reduces your actual debt — the other £99 goes straight to the lender.
By month 48 of the same loan, the interest charge has fallen to under £3 because the balance is so low. Almost your entire final payment is principal. This gradual shift is called amortisation — and understanding it explains why overpaying early in a loan is far more powerful than overpaying near the end.
Every pound you overpay reduces the balance on which all future interest is calculated. Overpaying £100 in month 6 of a 48-month loan saves significantly more interest than the same £100 overpaid in month 40 — because it compounds across far more future months. The earlier you pay extra, the bigger the saving.
The crossover point is the specific month when your principal repayment first exceeds your interest payment for that month. It is the moment the loan tips from being lender-weighted to borrower-weighted — when more of your fixed payment goes toward reducing debt than toward paying interest.
For a £15,000 loan at 7.9% APR over 48 months, the crossover typically falls around month 25. Before that point, you have paid the lender proportionally more than you have reduced your debt. This is why the crossover month is one of the most strategically important numbers in any loan — particularly if you are considering refinancing, consolidating or making a lump sum payment.
If you refinance a loan before the crossover point, you have paid mostly interest and still owe most of the principal. The new loan resets the clock entirely. Refinancing after the crossover is usually more favourable — though you must still compare total remaining interest on the old loan versus the new loan’s total cost.
Making a lump sum payment before the crossover has the greatest impact because it reduces the balance at the point where the most future interest is still to be charged. A £1,000 lump sum in month 6 of a 4-year loan can save over £300 in interest — compared to perhaps £60 if made in month 42.
The higher your interest rate, the later the crossover falls. A 3.5% APR loan crosses over around month 18 of a 36-month term. A 24.9% APR loan on the same term may not cross over until month 28 or later. This is one of many reasons why improving your credit score before borrowing has such a large financial impact.
Extending a loan term pushes the crossover point further into the loan. A 7-year loan at the same rate crosses over much later than a 3-year loan — meaning you spend more of the loan duration in the lender-weighted phase, paying more total interest for the lower monthly payment.
The table below shows the year-by-year interest and principal split for a £15,000 loan at 7.9% APR over 4 years — the default values in the calculator above.
| Year | Interest Paid | Principal Paid | Total Paid | Balance Remaining | Debt Cleared |
|---|---|---|---|---|---|
| Year 1 | £971 | £3,403 | £4,374 | £11,597 | 22.7% |
| Year 2 | £718 | £3,656 | £4,374 | £7,941 | 47.1% |
| Year 3 | £447 | £3,927 | £4,374 | £4,014 | 73.2% |
| Year 4 | £155 | £4,014 | £4,169 | £0 | 100% |
| Total | £2,291 | £15,000 | £17,291 | — | 100% |
Of the £17,291 paid in total, £2,291 (13.2%) goes to interest. Year 1 is the most expensive in interest terms at £971. By Year 4, only £155 is charged in interest — less than one-sixth of Year 1’s interest charge. This is the amortisation effect made visible.
If you are offered a debt consolidation loan 18 months into a 4-year term, check your current loan’s remaining interest before agreeing. You may have already paid £1,500 in interest and only have £800 left to pay. A new loan — even at a lower rate — restarts the amortisation clock and could cost more total interest than staying put. Always use the total remaining interest figure, not just the monthly payment.
This breakdown tool is most powerful when used alongside the other calculators in this category. Here is how they connect:
Before borrowing: Use the Loan Eligibility Calculator to check approval chances and maximum amount, then the EMI Calculator to see the exact monthly cost. Then use this tool to understand the interest burden across the full term.
During the loan: Use the crossover point shown here to identify the optimal timing for a lump sum payment. Use the Early Repayment Savings Calculator to quantify exactly how much interest a specific overpayment would save.
When considering consolidation: Check the remaining interest on your current loan using this tool. Then compare it against the total cost of the new consolidation loan using the Debt Consolidation Savings Calculator to confirm it genuinely saves money.
The crossover point is the specific month when your principal repayment first exceeds your interest payment for that month. Before this point, more of your fixed payment goes to the lender as profit than to reducing your debt. After it, the balance tips in your favour and your debt falls faster. The crossover is particularly relevant when timing lump sum payments, refinancing decisions or overpayment strategies.
Interest is calculated as a percentage of your outstanding balance each month. In month one, you owe the full loan amount, so the interest charge is at its highest. As payments reduce the balance, the monthly interest charge falls. But because the monthly payment stays constant, each month more of it is available to reduce the principal. By the final months of a loan, almost the entire payment is principal.
The earlier in a loan you make a lump sum overpayment, the more interest you save — because reducing the balance early means all future monthly interest charges are calculated on a lower amount. Overpaying in the first third of a loan typically saves 2–3 times more interest than the same payment in the final third. Use the Early Repayment Savings Calculator to quantify the exact saving for any payment amount at any point.
Yes, significantly. A higher rate means more interest is charged each month, which keeps the interest component of each payment higher for longer — pushing the crossover further into the loan term. A 5% loan may cross over around month 18 of a 36-month term. A 25% loan on the same term may not cross over until month 28 or later, meaning you spend more of the loan duration in the lender-weighted phase.
No — it changes every single month, which is exactly what this tool visualises. The total monthly payment (EMI) stays constant, but the proportion going to interest falls and the proportion going to principal rises with each payment. In month 1 of a £15,000 loan at 7.9% APR, around 27% of the payment is interest. By month 48, less than 1% is interest.
Yes. The underlying mathematics is identical — mortgages use the same amortisation formula as personal loans. Enter your mortgage balance, your current interest rate (use your fixed or tracker rate) and the remaining term in months. For a 25-year mortgage with 20 years remaining, enter 240 months. Note that when your fixed rate expires and you remortgage to a new rate, recalculate with the updated figures.