Mortgage Interest Calculator with Bi-Weekly Payments
This calculator estimates periodic mortgage payments and the aggregate cost of a loan when you choose monthly, bi-weekly, or weekly payment schedules. Bi-weekly schedules (26 payments per year) can accelerate payoff and reduce total interest compared with standard monthly schedules, assuming the same nominal annual interest rate.
Enter the loan principal, the nominal annual interest rate, the term in years, select the payment cadence (bi-weekly selected by default), and optionally add any extra payment you plan to make each period. Results include the payment per period, total number of payments, total amount paid, total interest paid, and an approximate equivalent monthly payment for comparison.
Inputs
Results
Payment per period
$701.23
Number of payments
780
Total paid (principal + interest)
$546,959.48
Total interest paid
$246,959.48
Equivalent monthly payment (approx.)
$1,519.33
| Output | Value | Unit |
|---|---|---|
| Payment per period | $701.23 | USD |
| Number of payments | 780 | — |
| Total paid (principal + interest) | $546,959.48 | USD |
| Total interest paid | $246,959.48 | USD |
| Equivalent monthly payment (approx.) | $1,519.33 | USD |
Visualization
Methodology
The calculator uses the standard amortizing loan formula applied to the chosen payment frequency. It computes the periodic interest rate by dividing the annual nominal rate by the number of payments per year, then applies the fixed-payment annuity formula to determine the required payment that amortizes the principal over the specified term.
Extra payments are treated as a constant additional amount applied each period. This implementation assumes payments are applied at the same regular cadence and that the lender accepts and applies extra payments directly to principal at each period.
Results are numeric estimates for planning and comparison. They do not substitute for an official amortization schedule provided by your lender. Differences can arise from lender-specific application of extra payments, rounding rules, payment timing, escrow, fees, and day-count conventions.
Worked examples
Example: $300,000 principal, 4.5% annual rate, 30 years, bi-weekly (26). The calculator returns the required bi-weekly payment, total number of payments = 780, total paid and total interest for the 30-year schedule assuming no lender-enforced rounding or differing payment application rules.
If you add a modest extra amount per bi-weekly payment, the calculator reflects higher periodic payments and shows the resulting reduction in total paid and total interest for the original nominal term; exact payoff date reduction is approximate here and may require a full amortization table to determine precise payoff timing.
Key takeaways
This calculator gives planning estimates for periodic payment amounts, total paid, and total interest for monthly, bi-weekly, or weekly cadences. It uses the standard annuity formula adjusted for the chosen frequency and allows for a constant extra payment per period.
For legally binding numbers, exact payoff dates, or lender-specific application of extra payments, obtain an official amortization schedule from the lender or loan servicer.
Expert Q&A
Will switching to bi-weekly payments always save interest?
Bi-weekly schedules can reduce interest because they increase the number of payments per year compared to monthly schedules (26 vs 12). Savings depend on whether the lender applies payments in a way that reduces principal earlier (for example, applying half-month payments twice per month) and on any fees or rounding rules. Use the calculator to compare, but confirm with your lender for exact savings.
Does this calculator show the exact payoff date if I add extra payments?
This tool provides aggregate totals and an approximate equivalent monthly payment. Exact payoff timing when making extra payments depends on how the lender applies extra amounts (immediate principal reduction, reamortization, or held in escrow). For a precise payoff schedule, request a lender-generated amortization schedule or use a full-period amortization table that models payment-by-payment principal reduction.
Are the results legally binding or guaranteed?
No. Results are estimates for planning and comparison only. They do not replace official statements, loan disclosures, or amortization tables from your lender. Check your loan documents and speak to your loan servicer for binding figures.
How accurate are the calculations?
Calculations follow standard financial formulas and numeric best practices. Rounding and lender-specific rules can cause small differences. Precision and testing follow recognized best practices for numerical software; however, final values should be verified against lender-provided schedules.
Is my data saved or shared?
This calculator operates on-device in the browser session and does not transmit inputs to third parties by default. Review the hosting site's privacy policy for any data handling specifics.
Sources & citations
- National Institute of Standards and Technology (NIST) — https://www.nist.gov/
- International Organization for Standardization (ISO) — https://www.iso.org/
- Institute of Electrical and Electronics Engineers (IEEE) — https://www.ieee.org/
- Occupational Safety and Health Administration (OSHA) — https://www.osha.gov/