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Put two fixed-rate installment scenarios side by side for the same stairlift purchase. See how the term, interest and fees change what you would pay.

Use a fixed contractual interest rate, not APR.

APR includes certain fees as well as interest; this model enters fees separately. CFPB explains the distinction. If only APR is stated, ask the lender for the contractual rate and payment schedule.

This is an educational illustration, not a credit offer, affordability assessment or lender disclosure. It cannot model deferred interest, changing rates, balloon payments or revolving credit.

1. Start with the same purchase

Use one complete, tax-inclusive cash price. If offers cover different equipment or work, reconcile the scope first. Do not include loan fees in this price.

Complete installed cash price ($)Equipment, fitting, tax and confirmed purchase charges, counted once.

2. Enter both payment plans

Every number is required. A blank field is unknown, not zero. Split fees by when they are paid; do not count the same fee twice.

Plan ADown payment ($)Enter 0 only when confirmed as zero or included elsewhere.Fees paid upfront ($)Enter 0 only when confirmed as zero or included elsewhere.Fees added to the loan ($)Enter 0 only when confirmed as zero or included elsewhere.Annual interest rate (%) — not APRFixed annual contractual interest rate, not APR. Enter 0 only for a confirmed 0% rate.Number of monthly paymentsWhole months, 1–180. Equal end-of-month installments assumed.

Plan BDown payment ($)Enter 0 only when confirmed as zero or included elsewhere.Fees paid upfront ($)Enter 0 only when confirmed as zero or included elsewhere.Fees added to the loan ($)Enter 0 only when confirmed as zero or included elsewhere.Annual interest rate (%) — not APRFixed annual contractual interest rate, not APR. Enter 0 only for a confirmed 0% rate.Number of monthly paymentsWhole months, 1–180. Equal end-of-month installments assumed.

I am comparing fixed-rate installment scenarios. These are not deferred-interest promotions, variable-rate loans or credit-card minimum payments.

What this calculation includes

Starting balance = cash price − down payment + financed fees. Cash due upfront = down payment + upfront fees. Total paid = cash due upfront + all modeled loan payments. The cost above the cash price includes the fees you enter and modeled interest.

For a positive rate, the unrounded installment is P × r ÷ (1 − (1 + r)⁻ⁿ), where P is the starting balance, r is the annual interest rate divided by 1,200, and n is the number of months. At 0%, it is P ÷ n. The model rounds the regular payment and each month’s interest to cents, then adjusts the final payment to clear the balance. Very small balances can clear earlier because of rounding.

Interest starts accruing for the first monthly period on the entire opening balance, including financed fees. Payments occur at each month’s end. There are no early, missed or extra payments, insurance charges, tax benefits, price changes or fees beyond those entered. Daily-interest and other lender methods can produce different figures.

Compare the lender’s actual APR, finance charge, total of payments, payment dates and fee disclosures separately. This tool does not calculate APR or determine which fees are legally included in it. Confirm any payoff conditions with the lender; no offer is recommended here.

Your entries stay on this page

The calculator does not send or save your figures. They are lost when you leave or reload. Print or download a copy to keep it. No name, address, income, account number or credit application is needed.

Definition reference: CFPB, loan interest rate versus APR; reviewed by CFPB August 28, 2026, checked October 25, 2026. The linked page uses auto loans as its example; this tool uses only the general rate distinction, not vehicle-loan rules. Independent financial review has not been completed.