Overpay Mortgage vs Invest Calculator
You've got a bit extra each month — should it go on overpaying your mortgage, or into an investment? Compare the interest you'd save by overpaying against the growth you might get by investing the same amount instead.
Estimate only. Estimate — assumes fixed growth/rates; investments can fall; not financial advice.
Enter your mortgage and extra amount
Add your mortgage balance and the extra monthly amount and we'll compare overpaying against investing.
Overpaying vs investing — the trade-off
Every pound you put toward overpaying your mortgage stops earning interest for the lender straight away — a guaranteed return equal to your mortgage rate, with no risk. Every pound you invest instead has the chance to grow faster, especially over a long time horizon, but that growth is never guaranteed: markets can fall as well as rise, and a bad run early on can leave you worse off than if you'd simply overpaid. This calculator runs both paths using the same fixed monthly amount, over the number of years you choose, so you can see the guaranteed interest saved by overpaying next to the projected (not guaranteed) growth from investing. If your mortgage rate is higher than your realistic expected investment return, overpaying usually wins outright; the closer the two rates are, the more it comes down to how much investment risk you're comfortable taking on.