Sri Lanka Credit Card Easy Payment Plan Calculator

Sri Lankan retailers advertise "0% easy payment plans", but the fine print almost always adds a one-time handling fee, or the plan carries a flat or reducing interest rate. This calculator converts whichever terms you are offered into a single, comparable number — the Annual Effective Rate (AER)— using standard, universally-defined finance mathematics. The CBSL Financial Consumer Protection Regulations No. 01 of 2023requires financial service providers to disclose the true cost of credit; this tool applies that same principle to a plan you are considering at the till.

The core idea is the internal rate of return (IRR). You receive goods worth the cash price P today and repay a schedule of installments. The true monthly rate r is the one that makes the present value of every payment equal P:

P = Σ installment / (1 + r)^t, for t = 1 … n

The tool solves this by bisection to eight decimal places, then annualises with AER = (1 + r)^12 − 1. It handles the three plan shapes you actually meet in Sri Lanka:

• 0% with handling fee. Total fee = P × fee%. If the fee is spread, each installment is (P + fee) ÷ n; if charged upfront, you pay the fee on day one and the installments discount against a smaller financed base — which makes an upfront fee cost slightly more than the same fee spread.
• Flat monthly rate. Interest is charged on the original amount every month: installment = P ÷ n + P × flat%. Because you keep paying interest on the full sum even as the balance falls, the AER is roughly double the flat rate.
• Reducing annual rate. The classic EMI on the outstanding balance:M = P·m·(1+m)^n / ((1+m)^n − 1), where m is the monthly rate. Here the AER is simply (1 + m)^12 − 1.

Every result is cross-checked against the constant-ratio ("N-ratio") nominal APR approximation, 2·n·C / (P·(n+1)), so the effective rate is corroborated by an independent method rather than a single solver. Finally, if you enter the return your cash could earn elsewhere — say an 8% fixed deposit — the tool compares it against the plan's AER and states, as plain arithmetic, whether paying cash or financing is cheaper. Everything runs in your browser; nothing is uploaded.

• CBSL — Financial Consumer Protection Regulations No. 01 of 2023 (true-cost disclosure)
• Central Bank of Sri Lanka — Financial Consumer Protection framework
• Central Bank of Sri Lanka — official site

The regulatory citation and the reducing-balance EMI / IRR formulae used here were last verified on 2026-07-16. Plan terms (amount, tenor, fee, rate) are your inputs, not a stored rate table, so the tool stays accurate for any current offer.