Biweekly vs Monthly Mortgage Payment Calculator

Biweekly schedules pay 13 monthly equivalents per year, not 12. That is the entire trick. There are 52 weeks in a year, so 26 biweekly half-payments equal 13 full monthly payments. The 13th payment goes straight to principal. Compounded over 25-30 years, that one extra payment per year cuts 5-7 years off a 30-year loan.

Three ways your servicer might run this, and they do not pay the same.

1. True biweekly. The loan itself accrues fortnightly and every half-payment reduces the balance the day it arrives. Rare in the United States, standard in Canada as “accelerated biweekly”. The biweekly mortgage savings calculator models this one.
2. Hold and apply annually. The servicer collects your half-payments, banks them, and puts one extra full payment against principal once a year. The loan stays a monthly loan. This is what the calculator on this page models, and it is the arrangement most US biweekly programs actually run.
3. Pure float. The servicer holds each half-payment until the monthly due date and applies nothing extra. No saving at all, and the bank earns on your money in the meantime.

On a $300,000 loan at 6.5% over 30 years, the first saves about $88,100 and the second about $84,000. Both cut roughly five years and nine months off the term. The third saves nothing, so ask which one you are being enrolled in.

Whichever it is, the enrollment fee is the part to argue with. A $5-10 monthly charge against a saving you can have for free is a bad trade: send one extra full payment in December, or add a twelfth of a payment to each monthly one, and you get outcome 2 with no fee and no float for the bank.

The math actually paid. On a $300,000 loan at 6.5% / 30 years:

• Standard monthly P&I: $1,896.20
• Total interest paid: $382,633
• Biweekly equivalent: 26 × $948.10 = $24,650/year, which is one extra monthly payment
• Biweekly total interest: $298,649
• Payoff: 24 years 4 months, so 68 months early
• Interest saved: $83,985

Put those three inputs into the calculator above and it returns exactly those figures.

Why it works so well. Mortgage interest is front-loaded. The first year of payments on a 30-year is mostly interest. Killing principal early dodges the most interest you would otherwise pay. A dollar of extra principal in year 1 is worth far more than a dollar in year 25.

The trap. Biweekly only beats monthly if you actually have the cash flow to make 13 payments of money. If you are stretched and switch to biweekly, the next time something breaks you are forced to skip, which wipes out the savings. Build the emergency fund first, then accelerate the mortgage.

Comparison to lump-sum prepayment. A single $20,000 prepayment in year 5 saves slightly more interest than 5 years of biweekly. Both work; pick whichever fits how you actually save money.