This is your marginal tax rate, the rate at which each additional dollar of income will be taxed. If you pay only Federal income taxes, it is the highest tax bracket you used when you calculated your taxes. Federal tax brackets currently are: 10%, 15%, 25%, 28%, 33%, and 35%. If you also pay state and/or local income taxes, these marginal rates can be added to the Federal rate. For example, if you had to pay 25% to the IRS and 5% to the state of Pennsylvania, your tax bracket is 30%. To perform a "pre-tax" analysis enter zero (0) as the tax rate.If you have not made any extra payments on your loan, this is the original term less the number of monthly payments that have been made. If you have made any extra payments, you can find the period remaining by clicking here and entering your current balance, rate, and monthly payment. Make sure the payment is principal and interest only. (hover over yellow icon to make this pop-up disappear)On old loans, the period remaining equals the original term less the number of monthly payments you have made, provided you have not made any prepayments. If you have made prepayments, go to the Monthly Payments on Fixed Rate Mortgages calculator, enter the payment and derive the current term.This is the interest rate you could earn on the monies you spend during the period you are in your home. For most people, it would be the interest rate on a bank account or a money market fund. In after-tax cost comparisons, this figure is adjusted to an after-tax basis.