This calculator will calculate the weekly payment and associated interest costs for a new mortgage.
Or, if you are already making monthly house payments, this weekly payment mortgage calculator will calculate the time and interest savings you might realize if you switched from making 12 monthly payments per year, to making the equivalent of 13 or 14 payments per year on a bi-weekly or weekly basis.
Plus, I recently added a field wherein you can enter an optional, extra weekly payment amount to be added to the calculated weekly payment amount. You'll be amazed at how much a small extra amount per week can save you in time and interest over the long run.
Finally, I have also recently added an "Estimated payoff date" row to the comparison results so you can immediately see the month and year each payment interval will pay off the mortgage.