Mortgage vs Invest Calculator

When you have surplus cash, you can overpay your mortgage (guaranteed return at your rate) or invest it (potentially higher but uncertain returns). Use this calculator for accurate, instant results.

The calculator uses the standard published formula for mortgage vs invest. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

This calculator works with inches, watts. You can enter values in the units shown — the calculator handles all conversions internally.

The core formula is: Mortgage saving = Extra payment x mortgage rate (compounded). Each step in the calculation is shown so you can verify the result manually.