This planner follows your financial future, calculating and graphing your pension and mortgage over time. It shows what might happen if you replace any mortgage overpayments with investments in the stock market instead. Just remember, it's not financial advice - you'll need an expert for that.
How the numbers grow
Pension contributions and invested overpayments are added at the start of each month, then grow at the annual rate converted to a compounded monthly rate. Contributions stay fixed in pounds. Returns are assumed to be after fees.
Your mortgage
The starting required payment is estimated over a 25-year remaining term, with a £100 monthly overpayment. You can edit both payments. The remaining term is inferred from your starting balance, current rate and required payment. The standard payment is recalculated each month against that original term. The overpayment path uses your fixed total payment and your future rate schedule. Mortgage rates use the same effective monthly conversion as the Python model, which may differ from a lender’s calculation.
The investment alternative
The difference between your total and required payment is invested every month for the entire projection, including after the mortgage is cleared. Released mortgage payments are not reinvested. The investment pot and interest saving are separate measures, so this is not a like-for-like comparison of total wealth.
Today’s money and the range
Today’s money discounts each future value by your inflation assumption. Future money shows the undiscounted pounds. Shaded ranges use your lower and upper assumptions; they are not statistical confidence intervals. A cautious outlook pairs lower investment returns with higher mortgage rates; an optimistic outlook does the reverse.
What’s outside the model
Taxes, tax relief, pension withdrawals, contribution increases, overpayment limits and charges, property value, and remortgage fees are not included. Savings are measured through the selected projection end date. The source model does not add unpaid interest to a mortgage balance; a warning appears if a payment fails to cover interest.
Saved just for you
Your inputs and named scenarios are stored in this browser when local storage is available. Export downloads a CSV with monthly results, your inputs, and the mortgage schedule. No account or connection is needed.