The mortgage payoff calculator helps you find out. Use the extra payment calculator below to help determine how advantageous it is to pay a little extra each month toward your mortgage.Free mortgage payoff calculator to evaluate options to pay off a mortgage earlier, such as extra payments, bi-weekly payments, or paying back altogether. This guide will help you learn mortgage math, allowing you to confidently calculate how much you need to pay off your mortgage. Homebuyer Assistance. Homeownership is a dream for many Houstonians but is out of reach for many residents. For Complete list of Payment Options Please click here.