Calculator Inputs
Example data table
This sample uses a $350,000 loan, 6.25% rate, 30-year term, $50 extra biweekly principal, and the half-month accelerated method.
| Payment # | Date | Payment | Interest | Principal | Remaining Balance |
|---|---|---|---|---|---|
| 1 | 2026-04-17 | $1,127.51 | $840.17 | $287.34 | $349,712.66 |
| 2 | 2026-05-01 | $1,127.51 | $839.48 | $288.03 | $349,424.64 |
| 3 | 2026-05-15 | $1,127.51 | $838.79 | $288.72 | $349,135.92 |
| 4 | 2026-05-29 | $1,127.51 | $838.10 | $289.41 | $348,846.51 |
| 5 | 2026-06-12 | $1,127.51 | $837.40 | $290.10 | $348,556.41 |
| 6 | 2026-06-26 | $1,127.51 | $836.70 | $290.80 | $348,265.61 |
Formula used
Monthly payment formula:
\( M = P \times \dfrac{r}{1 - (1 + r)^{-n}} \)
Here, P is loan principal, r is monthly interest rate, and n is total monthly payments.
Half-month accelerated biweekly formula:
Biweekly P&I = Monthly P&I / 2
True biweekly amortization formula:
\( B = P \times \dfrac{j}{1 - (1 + j)^{-26Y}} \)
Here, j is the equivalent biweekly rate and Y is the term in years.
All-in biweekly estimate:
All-in biweekly outlay = Biweekly P&I + (Annual Tax / 26) + (Annual Insurance / 26) + (Monthly HOA × 12 / 26) + Extra Biweekly Principal
How to use this calculator
- Enter your mortgage loan amount, interest rate, and term.
- Choose a first payment date for the amortization timeline.
- Add annual property tax, home insurance, and monthly HOA if needed.
- Enter any extra biweekly principal or upfront principal reduction.
- Select either half-month accelerated biweekly or true biweekly amortization.
- Click Calculate to view payoff date, interest, schedule, and chart.
- Use the CSV or PDF buttons to export your results.
Frequently asked questions
1. What is a biweekly mortgage payment?
A biweekly mortgage payment is made every two weeks, creating 26 payments each year. That timing can speed principal reduction compared with standard monthly payments.
2. What is the difference between half-month and true biweekly?
Half-month biweekly uses half of the monthly principal-and-interest payment. True biweekly calculates a direct biweekly payment for the same term. Half-month plans usually pay off faster because 26 half-payments equal 13 monthly payments annually.
3. Does paying biweekly save interest?
It often does. More frequent payments reduce balance sooner, so less interest accrues over time. Savings depend on rate, term, payment method, and any extra principal.
4. Are taxes and insurance part of loan amortization?
No. Taxes and insurance usually affect cash outflow, not principal amortization. This calculator adds them to the all-in biweekly estimate but keeps them outside the principal-and-interest schedule.
5. What does extra biweekly principal do?
Extra biweekly principal goes directly toward the loan balance. That usually shortens payoff time and lowers total interest paid across the mortgage.
6. Can I use this for a refinance scenario?
Yes. Enter the refinance loan balance, new rate, new term, and any added recurring costs. The schedule will estimate the updated payment path.
7. Why might lender results look different?
Lenders may use different posting dates, escrow handling, rounding rules, or payment processing policies. This tool gives a strong estimate, but the servicer’s exact schedule can vary slightly.
8. Does the calculator work for zero interest?
Yes. When the rate is zero, the calculator spreads principal evenly across the selected payment periods and still builds the schedule.