Home Loan Extra Payments Calculator with Bi-Weekly Payments
This calculator provides estimates for mortgage payments, payoff timing, and interest savings when making bi-weekly or other periodic payments and when adding extra principal payments (recurring or one-time). It models level-payment (fully amortizing) loans and assumes interest compounds per scheduled period.
Results are intended for planning and comparison only. Actual lender behavior, escrow, fees, prepayment penalties, and rounding can change exact outcomes. Verify final figures with loan documents or your lender.
Calculates the regular payment, total paid and total interest for a level-payment amortizing loan using the entered payments per year.
Inputs
Results
Scheduled payment (per period)
—
Number of payments (periods)
—
Total paid over life of loan
—
Total interest paid
—
| Output | Value | Unit |
|---|---|---|
| Scheduled payment (per period) | — | currency |
| Number of payments (periods) | — | periods |
| Total paid over life of loan | — | currency |
| Total interest paid | — | currency |
Visualization
Methodology
The tool computes a periodic interest rate by dividing the entered annual percentage rate by the number of payments per year. The base scheduled payment is derived from the level-payment amortization formula: payment = P * r / (1 - (1+r)^-N).
For recurring extras, the calculator increases the per-period payment and solves for the new number of periods using the closed-form logarithmic solution for an amortizing loan. For a one-time extra payment, the outstanding balance at the chosen period is computed and the reduced balance is re-amortized to estimate remaining payments.
Inputs must express payments per year explicitly (commonly 12 for monthly, 26 for bi-weekly). Using 26 models 26 identical periodic payments per year and the corresponding periodic rate; some lenders treat bi-weekly differently—check your loan terms.
Further resources
Expert Q&A
Does entering 26 payments/year always match my lender's bi-weekly program?
Not always. Entering 26 simulates 26 equal payments per year and the periodic interest rate that results. Some lenders accept accelerated bi-weekly plans differently or require enrollment. Check your loan documents for how payments are applied and whether extra payments reduce principal immediately.
Are results exact for legal or tax reporting?
No. This calculator provides estimates. For legal, tax, or closing figures rely on lender statements, official amortization schedules, or a licensed mortgage professional.
How accurate are the formulas?
Formulas implement standard amortizing loan mathematics (time value of money and closed-form solutions). They assume constant interest rate, no fees, and that extra payments are applied directly to principal at the stated period.
Sources & citations
- National Institute of Standards and Technology (NIST) — timeliness and numerical methods guidance — https://www.nist.gov
- International Organization for Standardization (ISO) — software quality standards reference — https://www.iso.org
- Institute of Electrical and Electronics Engineers (IEEE) — numeric stability and testing best practices — https://www.ieee.org
- Consumer Financial Protection Bureau — mortgage basics and prepayment information — https://www.consumerfinance.gov