Auto Loan APR Calculator with Bi-Weekly Payments

Calculations use standard annuity formulas to compute level periodic payments: Payment = P * r / (1 - (1 + r)^(-n)), where r is the periodic rate and n is the number of periods. For the standard bi-weekly method we divide the entered nominal annual rate by 26 to get the periodic rate and set n = years * 26.

The accelerated bi-weekly mode estimates results by halving the equivalent monthly payment and applying it on a bi-weekly cadence. This produces interest savings in practice because it increases the number of payments per year relative to monthly schedules, but the model here is an approximation and does not perform a full per-period amortization with early-payoff date shortening.

Precision and numerical behavior follow widely used floating-point and financial calculation practices. For transparency we flag effective annual rate computed as (1 + periodic_rate) ^ payments_per_year - 1. Regulatory APR under consumer lending law is a legal disclosure that may differ from the effective annual rate shown here.

Example 1: $20,000 loan, 5% APR, 5 years. Standard bi-weekly splits the rate into 26 periods to compute the bi-weekly payment and total interest. Accelerated bi-weekly splits the monthly payment and typically reduces total interest versus monthly payments.

Example 2: A borrower with $15,000, 6% APR, 4-year term and $300 fees can compare the estimated total paid under monthly, standard bi-weekly, and accelerated bi-weekly options to see potential savings before discussing exact terms with the lender.