Cernarus

Boat Loan Amortization Calculator with Bi-Weekly Payments

This calculator estimates amortization details for boat loans and allows direct comparison between monthly, split bi‑weekly, and true bi‑weekly payment approaches. Enter the loan amount, APR, term, and any regular or one‑time extra payments to see scheduled payment amounts, estimated payoff time and total interest.

Results are estimates for planning and comparison. They assume a fixed interest rate and consistent payments. Real loan contracts may include different compounding rules, fees, or prepayment policies that affect the schedule.

Updated Nov 27, 2025

Interest computed per bi‑weekly period (26 periods/year). This produces the accelerated payoff most commonly associated with true bi‑weekly schedules.

Inputs

Results

Updates as you type

Bi‑weekly scheduled payment

$157.06

Payment with regular extra

$157.06

Years to payoff (estimate)

10

Total interest (estimate)

$10,835.08

OutputValueUnit
Bi‑weekly scheduled payment$157.06currency
Payment with regular extra$157.06currency
Years to payoff (estimate)10years
Total interest (estimate)$10,835.08currency
Primary result$157.06

Visualization

Methodology

Calculations use discrete periodic amortization formulas: periodic_rate = APR / payments_per_year; payment = P * r / (1 - (1+r)^-N). For payoff estimates when regular extra payments are applied, the closed‑form logarithmic solution for N is used: N = -log(1 - P*r / payment) / log(1+r).

When 'bi‑weekly (split monthly)' is selected, the monthly amortization is computed first and then the monthly payment is split in two. For 'true bi‑weekly' the periodic rate and number of periods reflect 26 payments/year. Differences between these approaches come from how interest is applied and compounding frequency.

Worked examples

Example 1: $30,000 at 6.5% APR for 10 years. Monthly scheduled payment is computed with payments_per_year = 12. True bi‑weekly typically yields a lower total interest and shorter payoff time than splitting the monthly payment.

Example 2: Adding a $50 regular extra to each bi‑weekly payment reduces the payoff years and total interest; the calculator shows estimated periods to payoff and total interest saved compared to the base schedule.

Key takeaways

Use 'True bi‑weekly' to model lenders that compute interest per 26 periods/year. Use 'Bi‑weekly (split monthly)' to model the common case where the monthly payment is divided in two.

All outputs are estimates for planning. Verify with your lender for contract‑specific amortization, fees, and prepayment terms.

Expert Q&A

Why are there different bi‑weekly options?

Some lenders amortize monthly but accept bi‑weekly payments by splitting the monthly payment; this reduces principal faster than monthly payments but still uses monthly interest rules. True bi‑weekly amortization computes interest and amortization for 26 periods per year, producing the accelerated payoff typically associated with 'bi‑weekly' plans.

Are the results exact?

Results are mathematical estimates based on fixed-rate amortization formulas. They do not include lender fees, insurance, taxes, or varying compounding conventions. For exact payoff schedules, request an amortization table from your lender or examine the loan contract.

How do extra payments affect payoff?

Regular extras increase the effective payment, which reduces the number of periods needed to pay off the principal and lowers total interest. One‑time extras reduce principal immediately; the calculator approximates their effect by subtracting them from the balance in total paid calculations.

What about zero or extremely low interest rates?

If the periodic rate is zero, the scheduled payment simplifies to principal / N. The calculator formulas assume positive periodic rates; if APR is zero or nearly zero, results use the simplified linear payoff calculation. Very low rates may produce numerical instability; see accuracy caveats.

Sources & citations