Every extra pound you pay goes straight at the balance — and stops earning interest for your lender for decades. See how many years and how much interest an overpayment saves.
Most lenders let you overpay up to 10% of the balance each calendar year without early repayment charges — check your deal.
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Assumes your rate stays the same for the rest of the term and interest is charged monthly. Real deals change at the end of each fix — rerun the numbers when yours does. This is an illustration, not financial advice; nothing you enter is stored or sent anywhere.
Your monthly mortgage payment is mostly interest in the early years — on a typical £200,000 mortgage at 4.5%, around £750 of your first £1,112 payment is interest, not debt. An overpayment skips that queue entirely: every extra pound goes straight at the balance, and then saves you interest on itself every month for the rest of the term. That’s why just £100 a month clears the mortgage three and a half years early and saves over £21,000.
One honest caveat: overpaying isn’t always the best home for spare cash. Clear expensive debts first — a credit card at 24.9% costs five times what your mortgage does, and our card payoff calculator shows the damage. Keep an emergency fund too (see what regular saving grows into with the savings calculator), and if your savings rate beats your mortgage rate, saving can mathematically win while it lasts. Need to find the spare cash in the first place? Start with the bill-cutting checklist.
Compare the rates. If your mortgage charges 4.5% and your savings pay 5% after tax, saving wins mathematically — you can always throw the pot at the mortgage later (watching the 10% allowance). If your mortgage rate is higher, overpaying wins, and it’s guaranteed and tax-free. Whatever you do, clear expensive debts like credit cards first and keep an emergency fund you can actually reach.
During a fixed or discounted deal, most lenders charge a fee (typically 1–5% of the amount overpaid) if you repay too much too fast — but almost all allow up to 10% of the outstanding balance each year penalty-free. Once your deal ends and you’re on the standard variable rate, you can usually overpay without limit. Your exact allowance is in your mortgage offer document.
To get the savings this calculator shows, the term should shrink while your payment stays the same. If the lender instead recalculates a lower monthly payment, your total interest barely falls — you’ve just given yourself a small pay rise today at the cost of years of extra interest. Most lenders let you choose; say ‘reduce the term’.
Twice over. You’ll owe less, so you pay interest on a smaller balance at whatever the new rate is — and if the smaller balance drops you below a loan-to-value threshold (say from 80% to 75%), you qualify for a cheaper band of remortgage rates too.
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Before you commit that money to the mortgage, see what the same amount would grow to in a savings account.
