Boat Loan Calculator

Use this boat loan calculator to estimate your payment, total interest, and total paid from price, down payment, APR, and term. You can also add sales tax and one-time fees to see your real financed amount and cash due at purchase.

How to use our Boat Loan Calculator

1. Enter the boat purchase price and your down payment.
2. Enter the interest rate (APR percent) and the loan term (years).
3. Open Advanced options if you want to include sales tax and one-time fees in the math.
4. If you enable tax and fees, choose whether you are paying them up front or financing them.
5. If you want, enter an extra payment per month to see a faster payoff estimate and interest saved.
6. Choose Payments per year only if your loan is not monthly.
7. Click Calculate.
8. Read Financed amount and Cash due at purchase to double-check your deal setup, then review Monthly payment, Total interest, and Total paid.

Definitions

APR (annual percentage rate): The yearly interest rate used here as a nominal rate that is converted to a per-payment-period rate.

Amortized loan (amortization): A loan with a regular payment schedule where each payment includes interest and also reduces the balance, ending at $0 if you make all scheduled payments. [1]

Principal: The starting loan balance (amount borrowed), not counting future interest. [2]

Financed amount: The starting loan balance this calculator uses (purchase price minus down payment, plus any tax/fees you choose to finance).

Cash due at purchase: Money paid up front at signing, like down payment and any tax/fees you choose to pay up front.

Payments per year: How many payments you make each year (12 means monthly).

Methodology

1) Inputs and validation

Required inputs: purchase price must be greater than 0; down payment must be 0 or more; APR percent is required and must be 0 or more; term years must be greater than 0.

Optional inputs: one-time fees and extra payment must be 0 or more. Sales tax rate can be blank, but if tax/fees are enabled and the rate is blank, sales tax is not added and a note is shown.

2) Out-the-door items (tax and fees)

base_loan = max(0, purchase_price - down_payment)

sales_tax = purchase_price * (sales_tax_rate/100)

financed_amount = base_loan + (include_tax_fees ? (pay_tax_fees_upfront ? 0 : (sales_tax + one_time_fees)) : 0)

cash_due = down_payment + (include_tax_fees ? (pay_tax_fees_upfront ? (sales_tax + one_time_fees) : 0) : 0)

If down payment is greater than purchase price, base_loan becomes 0. The calculator sets payment and totals to 0 and shows a note that no loan is needed.

3) Rate per payment period and number of payments

r = (apr/100) / payments_per_year

n = term_years * payments_per_year

apr_per_period_percent = r * 100

4) Standard payment (amortized loan)

For an amortized loan, the required payment is usually the same each period, while the split between interest and principal changes over time. [1][2]

if r == 0: payment = financed_amount / n

else: payment = financed_amount * (r * (1+r)^n) / ((1+r)^n - 1)

total_paid = payment * n

total_interest = total_paid - financed_amount

5) Extra payment payoff estimate (optional)

When you add an extra payment, the calculator estimates how many periods it takes to reach a $0 balance by simulating payment-by-payment (an amortization schedule). It assumes your extra amount goes directly to principal.

p = payment + extra_payment

balance = financed_amount

for k = 1.. until balance <= 0: interest_k = balance*r; principal_k = p - interest_k; if principal_k <= 0 stop (N/A); balance = balance - principal_k

interest_with_extra = sum(interest_k)

interest_saved = total_interest - interest_with_extra

The loop uses an iteration cap to avoid infinite runs. If the cap is reached, or if the payment is not enough to cover interest (principal_k is 0 or negative), payoff time and interest saved are shown as N/A with a note telling you what to change.

Sources