Loan Payment Calculator — Monthly Payment and Total Interest
The monthly payment and what the loan costs in total, side by side.
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Short answer
A loan payment can be calculated for free in a web browser from three numbers on one line: the amount borrowed, the annual interest rate and the term. Equal instalments use the standard amortisation formula — the payment is P × i ÷ (1 − (1 + i)^−n), where i is the monthly rate and n the number of months — while equal-principal repayment gives the first payment, the last payment and the total. The total interest is printed next to the payment in both cases.
At a glance
| Accepts | Three numbers per line — amount, annual rate %, term |
|---|---|
| Produces | The payment, the total interest and the total repaid |
| Processing | In your browser |
| Price | Free, no limits |
| Account | Not required |
Three numbers in, and the two that matter out: the instalment, and what the loan costs over its whole life. They are printed together on purpose. The monthly payment is the number a longer term makes smaller while the total interest goes up, and comparing two offers on the instalment alone is exactly how that goes unnoticed.
The two methods are the pair a lender normally offers. Equal instalments keep every payment the same and front-load the interest. Equal principal repays the same slice of the loan each month plus interest on what is left, so the first payment is the largest and every one after it is smaller — less interest in total, more asked of you early. None of this is advice: the arithmetic is the arithmetic, and the decision is not a formula.
How to use it
- 1
Type the loan
Three numbers per line: the amount, the annual rate as a percentage, then the term. For example 500000 4.5 30.
- 2
Pick the method and the term unit
Equal instalments or equal principal; a term counted in years or in months.
- 3
Convert
Each line comes back with the payment, the total interest and the total repaid.
- 4
Copy the result
Copy to the clipboard, or download it as a text file.
Frequently asked questions
Should the rate be the monthly or the annual one?
The annual one, as a percentage: type 4.5 for 4.5% a year. It is divided by twelve to get the monthly rate, which is what a lender's schedule uses.
What is the difference between the two repayment methods?
Equal instalments keep the payment constant for the whole term, with the interest share largest at the start. Equal principal repays amount ÷ months every month plus interest on the outstanding balance, so the payment falls over time. For the same rate and term, equal principal costs less interest in total.
Does it work at 0%?
Yes. At a zero rate the amortisation formula divides by zero, so the payment is simply the amount divided by the number of payments.
Are fees, insurance and early repayment included?
No. This is the interest arithmetic on the three numbers typed in. Arrangement fees, compulsory insurance, offset accounts and the effect of overpaying all change the real cost, and none of them is derivable from an amount, a rate and a term.
Is this financial advice?
No. It is a calculator — the same formula a lender uses to build a schedule, with no view on whether any particular loan is a good idea.