The Pro version of Karl's Mortgage Calculator is an upgraded version of the free version, with the only difference being the removal of advertisements. This calculator allows users to calculate mortgage payments based on principal, interest, and term. It also offers the option to reverse calculate any one variable given the other three.

One useful feature of this calculator is the ability to enter a down payment amount or percentage, and it will show how large a mortgage is required. Additionally, users can see how the monthly payment changes when additional monthly or annual loan costs such as PMI, HOA, taxes, and insurance are factored in.

The calculator supports various types of mortgages, including Fixed and Adjustable Rate Mortgages (ARM) loans with up to five changes in interest rates. It also supports interest-only mortgages. Users can pay off their mortgage early by making extra payments, including one-off, monthly, and annual extra payments. The calculator allows users to choose up to six additional extra payment amounts and payment periods, and it will show how much money can be saved on the loan.

Furthermore, the calculator offers flexibility in terms of loan payments and compounding periods. Users can choose from weekly to annual loan payments and adjust the compounding period from daily through annual periods. It supports Canadian mortgages and UK annual rest mortgages. Multiple rounding options are available for loan calculations, including no rounding, round half up, half down, to even, to ceiling, and to floor. The calculator also supports the input and display of multiple currencies.