See months saved and interest saved from extra monthly payments

When overpaying a loan is free money

A loan at 8% APR is costing you 8% a year on the outstanding balance. Overpaying that loan is effectively earning 8% guaranteed, low-risk, tax-free. That return is hard to beat anywhere else. A typical easy-access savings account pays 4–5%. A balanced investment portfolio averages 4–5% real. Overpaying mid-rate consumer debt therefore usually outperforms saving or investing on a risk-adjusted basis. The calculator above shows how much interest you save and how much earlier you're free of the loan.

The math of front-loaded interest

Standard amortisation means early payments are mostly interest. On a 10,000 loan at 8% over 5 years: first payment is 67 interest, 136 principal. Last payment is roughly 1 interest, 202 principal. The balance shrinks quickly in the final year because by then most of each payment is going to principal. This structure has a practical consequence: overpayments early in the loan save dramatically more interest than overpayments late. 500 overpaid in month 6 saves about 180 in interest over the loan life. The same 500 in month 54 saves under 20. Timing the overpayment as early as possible is roughly 10x more valuable than timing it as late.

Lump sum versus regular overpayment

Two strategies: a single 2,000 overpayment today, or 100 extra monthly for 20 months. Mathematically, the lump sum wins — the money starts reducing the balance immediately, so interest saved compounds from day one. Behaviourally, the regular overpayment is easier to actually execute for most people because it doesn't require finding a 2,000 windfall. If you have the lump sum available, use it; if you don't, regular overpayments are the practical path. Both save meaningful interest; the lump-sum version saves slightly more.

Check for early-repayment charges first

Regulated personal loans typically allow overpayments penalty-free within limits (often 8–10% of balance per year without charge). Larger overpayments or full early settlement can trigger an early-repayment charge — under the Consumer Credit Act, capped at 1–2 months' interest on the repaid amount. For a 10,000 early settlement at 8%, that's 130–260. Still usually worth it for the interest saved, but check the specific charge before transferring the money. Some older loan products have uncapped charges that make early payoff uneconomic; these are rare now but still exist.

Where overpaying doesn't win

The overpaying-wins logic depends on comparing against realistic alternatives. If the alternative to overpaying is keeping the money in a 4.5% easy-access account, the 8% loan overpayment wins cleanly. If the alternative is a workplace pension with employer match, the pension wins: 100%+ instant return from the match usually beats any consumer loan rate. If the alternative is maxing an tax-advantaged savings account that would grow at a historical 6–7% over decades, it's close — the loan rate usually wins on a rate basis, but the pension/tax-advantaged savings account money stays accessible for other purposes.

The hierarchy of spare money

For most households, the order is:

1. Minimum debt payments on everything — non-negotiable.

2. Small emergency fund (1,000) — before any overpayment, to avoid forcing yourself back to borrowing for an emergency.

3. Pension to the employer match — typically 100%+ instant return.

4. High-interest debt (credit cards, payday) — 20%+ returns from paying down.

5. Mid-interest debt (personal loans, car loans) — 6-12% returns from paying down.

6. Full emergency fund to 3-6 months — insurance against forced borrowing.

7. Pension above the match, up to annual allowance — tax-advantaged growth.

8. tax-advantaged savings account up to annual allowance — flexible tax-advantaged growth.

9. Low-interest debt overpayment (mortgage) — 4–6% returns, competes with tax-advantaged savings account/pension.

10. Non-tax-advantaged investment — when tax-advantaged space is used.

A mid-rate personal loan overpayment usually sits in position 5. The calculator here assumes you've already covered positions 1–4.

The psychological win of being debt-free

This is real even though it doesn't show up in calculations. Being free of consumer debt changes financial decision-making in subtle but measurable ways. Cash flow becomes more flexible. Emergency events stop cascading into worse debt. The mental bandwidth previously occupied by tracking balances gets freed up. For many people, these behavioural dividends are worth accepting a slightly sub-optimal pure-math position. The calculator quantifies the money; the quality-of-life gain from early payoff is real but unquantifiable.

What the calculator assumes

Standard amortisation, fixed interest rate, a single clean overpayment or extra monthly amount, and no early-repayment charge. Real loans vary. If your loan has a penalty, subtract it from the savings figure to get the honest net benefit. If the rate is variable and you expect it to rise, overpayment is more valuable than the tool suggests. If it's expected to fall, slightly less so.