How to use it:

1. Enter your loan details — original loan amount, mortgage rate, monthly principal & interest payment, and how many years until your rate resets (or your target payoff deadline).

2. Enter your portfolio details — the brokerage account's current value and its cost basis (what you originally invested, before growth). The gap between these two numbers is what determines how much tax you'll owe when you sell.

3. Adjust the two toggles — pick an expected annual return (7% or 10%) and whether NIIT (the 3.8% surcharge on investment income for higher earners) applies to your household.

4. Read the result — the tool shows the earliest month your after-tax portfolio value could exceed your remaining mortgage balance, plus a comparison across all four return/tax combinations, so you can see how sensitive the timeline is to your assumptions.