Mortgage & Investment

Compare scenarios, year by year.

How it works

Each scenario has its own investment and mortgage inputs. Income, spending and the chosen investment amount are monthly; whatever you choose to invest each month goes into the portfolio and grows at the scenario's ROI. Use the small →all button next to any field to copy its value to every scenario. Investment and mortgage can be switched off, the mortgage can start in any year (year 0 is the start of the analysis, matching the graph), and events change income, spending, investment, rate, or ROI from a given year. Your inputs are saved in this browser automatically.

Scenarios

Net worth over time

Summary

Metric

Yearly portfolio value

Details

Toggle full year-by-year breakdown per scenario.

Monte Carlo simulation

Simulates net worth trajectories by treating ROI, interest rate, income, and spending as random variables with the volatilities below. Shows the median line and the 10th–90th percentile band per scenario.

Important information

Privacy policy

This calculator runs in your browser. The calculator itself does not send your scenario inputs, calculations, or simulation results to a server.

Your scenarios, preferences, and settings are saved in your browser's local storage so they can be restored when you return. This information stays on this device and browser unless you clear it, use browser tools that remove site data, or otherwise share access to your browser profile. Private browsing may not retain it.

Clearing this site's local storage will remove the saved calculator data. This calculator does not require an account.

Financial disclaimer

This calculator is provided for informational and educational purposes only. It is not financial, mortgage, investment, tax, legal, or other professional advice.

Results are estimates based on the inputs and assumptions you provide. They are not loan offers, rate quotes, guarantees of investment performance, or predictions of future results. Actual outcomes may differ substantially.

The calculator does not automatically account for every possible cost or circumstance, including taxes, insurance, maintenance, closing costs, fees, inflation, changing market conditions, lender rules, or changes in personal income and expenses. Consult qualified professionals before making financial decisions.

Calculation methodology

Mortgage: The initial mortgage principal is property value minus down payment, floored at zero. The mortgage uses a standard amortizing-payment formula. Interest is applied monthly using the annual rate divided by 12, and principal and interest are tracked month by month.

Cash flow and portfolio: At the mortgage start year, the down payment is deducted from starting assets. Each month, income, spending, and the selected investment amount are applied. The investment contribution is limited to the money available after spending and mortgage payment; if there is a shortfall, the portfolio can become negative. Portfolio growth compounds monthly using the entered annual ROI converted to a monthly rate.

Events: An event changes its selected income, spending, investment, interest-rate, or ROI input from the chosen year. A rate change recalculates the payment over the remaining mortgage balance and months. Lump-sum mortgage payments are taken from the portfolio and capped at the amount available.

Net worth: Net worth is calculated as portfolio value plus the property value after the mortgage starts, minus the remaining mortgage balance. The main chart plots net worth by year.

Monte Carlo: Each simulation applies random annual shocks to the selected ROI, interest rate, income, and spending volatilities. The chart shows the median simulated path and the 10th–90th percentile range. These scenarios are illustrative, not forecasts.