Instalment plan calculator
The monthly payment on an instalment plan with a markup, plus the schedule.
Fill in the fields and the result will appear here automatically.
This model spreads the price less the down payment across monthly instalments after a one-time markup. A 12% markup means multiplying the financed amount by 1.12, not 0.12. Interest does not accrue on the remaining balance. That is the arithmetic chosen here, not a legal distinction between instalment plans and loans: real products can include interest, fees and other terms. Zero markup gives zero overpayment in this model.
How it works
Formula and logic
F=price−down payment, rounded to two decimals. Total T=F×(1+m/100) is rounded to two decimals too. The regular payment is T/n rounded to two decimals; the final payment clears the remainder so the schedule sums to T. If a tiny total cannot cover n−1 rounded payments, the regular payment is rounded down to whole cents and the remainder goes into the last one. Balances use integer cents; n is a whole number from 1 to 60. Contract fees and early-settlement recalculation are not modelled.
Example
A 60,000 purchase with 10,000 down over six months at a 12 % markup gives a payment of 9,333.33 and an overpayment of 6,000. Rounding boundary: price 0.04, no down payment or markup, six months. The first five regular payments are 0.00 and the last is 0.04: total 0.04, with no negative payment.
Fields and units
- Price — $
- Down payment — $
- Term, months — months
- Markup — %
How to use
- — Enter the purchase price and the down payment.
- — Give the term and the retailer markup.
- — Read the payment and the schedule.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- CFPB, United States: BNPL is installment credit with varying schedules and possible fees
- Limitation
- Markup is applied once to the financed amount. It is not an annual interest rate, effective cost or legal classification; servicing fees, late charges and early payoff are not modeled separately.
FAQ
How is an instalment plan different from a loan?
Here markup is applied once to the financed amount and no interest accrues on the balance. A real instalment plan can legally be a loan and use another scheme. The contract determines early settlement and any refund of markup; this calculator does not compute them.
How do I model an interest-free plan?
Leave markup at zero: the total equals the financed amount and model overpayment is zero. Comparing with payment upfront still requires checking the product price, fees and insurance in the contract.
Why is the final payment a few kopecks different?
Because the total rarely divides evenly across the term. The remainder goes into the last payment, otherwise the payments would not add up to the price.
Are insurance or fees included?
No. Add an expense to the price only if the same markup and schedule apply to it. A separately paid fee or insurance charge with different timing belongs in total costs outside this schedule.