This Maine biweekly mortgage calculator shows how much interest you save and how many years you cut off your loan by paying half your monthly payment every two weeks — using full period-by-period amortization for both schedules, not a rule of thumb.
How it works
First the tool computes your scheduled monthly principal-and-interest payment with the standard amortization formula:
M = P * r * (1 + r)^n / ((1 + r)^n - 1)
where P is the loan, r is the monthly rate (annual / 12), and n is the number of months. It then runs two amortization schedules:
- Monthly — the scheduled payment once a month, 12 payments a year.
- Biweekly — half the monthly payment every 2 weeks. There are 26 two-week periods in a year, so you make 26 half-payments, which equals 13 full monthly payments instead of 12. The biweekly periodic rate is the annual rate divided by 26.
For each schedule the tool sums the interest paid and counts the periods until the balance reaches zero, then converts biweekly periods to an equivalent number of months. The difference gives your years saved and total interest saved (monthly interest minus biweekly interest).
Example
A $320,000 Maine mortgage at 6.5% over 30 years has a scheduled payment of about $2,023/month, so the biweekly payment is about $1,011 every 2 weeks. Paid monthly, the loan runs the full 30 years and costs roughly $408,142 in total interest.
Switch to biweekly and the loan pays off in about 24 years 2 months — cutting off roughly 5 years 10 months and saving about $93,997 in interest, all from the single extra monthly-equivalent payment the 26-payment schedule produces each year.
Notes
This is an estimate only and not financial advice. It assumes a fixed interest rate and that your servicer applies each biweekly half-payment to principal immediately — some servicers hold the half-payment until a full monthly payment accrues, which eliminates most of the benefit, and some charge a fee to set up a biweekly plan. You can usually get the same result for free by dividing one monthly payment by 12 and adding it as extra principal each month. Property tax, insurance, and escrow are excluded. Confirm terms with your Maine lender before enrolling.