Biweekly Payment Calculator: Payoff Time and Interest Saved

This calculator shows what happens if you pay half of your monthly payment every two weeks instead of the full payment once a month. That makes 26 half-payments, the same as 13 monthly payments a year, so the loan ends sooner. Enter the amount, APR and term of the monthly loan.

Formula

Monthly payment M = P × r ÷ (1 − (1 + r)⁻ⁿ), r = APR ÷ 1200. Biweekly payment h = M ÷ 2 with rate i = APR ÷ 2600 per two-week period. Periods to pay off N = −ln(1 − i × P ÷ h) ÷ ln(1 + i); years = N ÷ 26. Interest saved ≈ M × n − h × N.

Worked Example

$250,000 at 6.5% APR over 30 years.

1. M = 1,580.17 a month, so h = $790.09 every two weeks
2. i = 6.5 ÷ 2600 = 0.0025; N = −ln(1 − 0.0025 × 250,000 ÷ 790.09) ÷ ln(1.0025) ≈ 627.05 periods
3. Years = 627.05 ÷ 26 = 24.1
4. Interest saved ≈ 1,580.17 × 360 − 790.09 × 627.05 = $73,434.87

Assumptions

• Fixed rate; interest charged every two weeks at APR ÷ 26 on the biweekly plan.
• Some lenders hold biweekly payments and apply them monthly; then the saving comes only from the 13th payment a year and is a little smaller.
• No fees for the biweekly plan.

How to read the result

The saving comes from paying one extra monthly payment a year. You can get almost the same effect by adding one twelfth of a payment to each monthly payment.

Limits and common mistakes

• Check with your lender that biweekly payments go straight to principal; some programs charge a fee.
• The saving shown is rounded through a fractional last period, so it is approximate.

Frequently Asked Questions

How much faster is a 30-year loan paid biweekly?

At 6.5%, in about 24.1 years instead of 30.

Why does it work?

26 half-payments a year equal 13 full monthly payments, one more than a monthly schedule.

Is it the same as weekly payments?

In effect, yes: a quarter of the monthly payment every week adds up to 13 monthly payments a year, the same as biweekly. A weekly payment worked out on its own 52-a-year schedule (the weekly vs monthly calculator) does not speed up the payoff.

in p | Loan amount | $ | 250000 | 1 | 100000000
in apr | Interest rate (APR) | % | 6.5 | 0.01 | 100
in yrs | Loan term | years | 30 | 1 | 50
out yb | Years to pay off with biweekly payments | years | -ln(1 - (apr / 2600) * p / (p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) / 2)) / ln(1 + apr / 2600) / 26 | 1
out hp | Biweekly payment (half the monthly) | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) / 2 | 2
out sav | Interest saved (approx.) | $ | hp * 2 * yrs * 12 - hp * yb * 26 | 2