About this tool
The Loan Calculator works out the fixed monthly payment, the total interest and the full repayment schedule for a single loan in Cambodia, in riel or US dollars. Enter the amount, the term in months or years and the annual rate, and the page returns the payment, the total cost and a month-by-month amortisation table you can export as CSV; two optional fields add an extra monthly payment and an origination fee expressed as a percentage of the loan. It is for the ordinary cases — a personal loan from a bank, a moto or car financed through a dealer, a home loan, a staff loan from an employer — and for checking a payment a lender has already quoted. It computes reducing-balance interest only: interest is charged on the balance still outstanding each month, which is the method National Bank of Cambodia Prakas №B-7-01-115 requires microfinance institutions and rural credit operators to use. It does not compute a flat-rate offer, where interest is charged on the original principal for the whole term and the same advertised percentage costs more; the loan offer comparison tool does that. It does not model insurance, a variable rate, a grace period, late fees or a balloon payment, it does not convert between currencies, and it quotes no lender rate. None of it is credit advice.
How it works
The arithmetic lives in `loan-calculator-client.tsx`, in the `calculations` memo, not in the shared `lib/finance/loan-calculations.ts` module. The origination fee percentage is applied to the amount you entered and the result is added to the principal, so a 1% fee on a 50,000 loan becomes a 50,500 principal and interest is charged on all of it. The monthly rate is the annual rate divided by 12, and the payment is the standard annuity formula M = P × r × (1+r)ⁿ ÷ ((1+r)ⁿ − 1); at a 0% rate it falls back to principal ÷ months. The schedule walks the term one month at a time, charging interest on the opening balance, adding any extra monthly payment to the principal part, and capping the principal part at the remaining balance, so the last payment is smaller rather than negative. Total interest is total paid minus principal, and the pie chart splits the two. The currency selector only changes the symbol and the decimal places — riel shows whole numbers, dollars show two decimals — it does not convert an amount from one currency to the other. The term field accepts 1 to 600 months or 1 to 50 years, the rate accepts 0 to 100%, and a blank or invalid field stops the results with a message instead of showing a figure.
Use cases
- A borrower checking the monthly payment a bank quoted on a 50,000 dollar, five-year personal loan
- A family testing what a 1% origination fee adds to the cost of a home loan over ten years
- A moto buyer comparing a dealer finance quote against the same amount borrowed from a bank
- An employee deciding whether to pay an extra 100 dollars a month and how much interest that saves
- An accountant reproducing a lender amortisation table to confirm the interest charged in year one
- A teacher or trainer showing why a 0% rate and a 24% rate produce very different schedules
- A small business owner planning a working-capital loan in riel and checking the total cost before signing
Frequently asked questions
How is the monthly payment calculated?
With the standard annuity formula for a fixed-rate, reducing-balance loan: M = P × r × (1+r)ⁿ ÷ ((1+r)ⁿ − 1), where P is the principal including any origination fee, r is the annual rate divided by 12 and n is the number of months. The payment is set so the balance reaches zero at the last month. At a 0% rate the formula divides the principal by the number of months instead, which is the same result without the interest term.
Does this calculator use flat or reducing-balance interest?
Reducing balance, and only reducing balance. Interest is charged each month on the balance still outstanding, so the interest part falls as the loan is paid down. There is no field to switch methods. If a lender has quoted you a flat rate — interest charged on the original principal for the whole term — this page will understate the cost, because it will treat that percentage as a reducing-balance rate. Use the loan offer comparison tool for a flat quote.
What is flat interest, and why can it cost more?
Flat interest is calculated once on the original principal and spread evenly across the months, so you pay the same interest in month 60 as in month 1 even though most of the principal is already repaid. On a 50,000 dollar loan over 60 months, 8% flat means 20,000 dollars of interest; 8% reducing balance on the same loan means 10,829 dollars. The advertised percentage is identical and the flat loan costs almost twice as much. Prakas №B-7-01-115 requires microfinance institutions and rural credit operators to charge on the outstanding balance, which is why a compliant MFI quote is normally a reducing-balance quote.
Can I use it for both riel and dollar loans?
Yes, but the currency selector is a display setting only. It changes the symbol and whether decimals are shown; it does not convert anything. A 50,000 riel loan and a 50,000 dollar loan are the same number to this calculator and very different amounts of money, so enter the figure in the currency the loan is written in and read the result in the same currency. The page never fetches an exchange rate.
What does the origination fee actually do?
It is added to the principal before the payment is computed, so the fee is treated as borrowed money and interest is charged on it for the whole term. A 1% fee on a five-year loan at 8% therefore costs more than 1% of the loan: you pay interest on the fee for sixty months. The fee is not deducted from the cash you receive in this model, which is how a financed fee works rather than an upfront fee paid at disbursement.
Why is the last payment smaller than the others?
Because the schedule caps the principal part of each payment at whatever balance remains. The fixed payment is calculated to clear the loan exactly over the term, but once an extra monthly payment is added the balance falls faster than the schedule assumes, so the final month needs less. Without an extra payment the difference is usually a few riel or cents from rounding, and with one it can be a large part of the payment.
Does the calculator include insurance, stamp duty or other bank fees?
No. The only fee field is the origination percentage, and it is financed into the principal. Credit-life insurance, property valuation, stamp duty, a monthly service fee and any penalty for early repayment are outside the model, and several of them are charged as a lump sum at signing rather than spread over the term. Add them to the total cost yourself before comparing two offers, or use the loan offer comparison tool, which has separate upfront, financed and monthly fee fields.
Is this an official calculator, or a loan offer?
Neither. It is an unofficial calculator built from the standard amortisation formula, it fetches no lender data, and it cannot approve, price or offer credit. The rate you type is your assumption, not a quote. Your bank or microfinance institution will apply its own rate, fees, insurance and rounding, and the contract it writes is the only figure that binds either side.
Data and accuracy
Nothing is fetched: the page uses the amount, term, rate, fee and extra payment you type, and the standard fixed-rate annuity formula in `loan-calculator-client.tsx`. The tool does not know any lender rate and does not read loan products from a bank. The reducing-balance rule it follows is the one in National Bank of Cambodia Prakas №B-7-01-115 on the calculation of interest rate on microfinance loans, which requires interest to be charged on the loan outstanding balance and a credit amortisation table to be part of the loan agreement. Content checked against that instrument on 21 October 2026.
Sources
Content last reviewed 21 October 2026