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Calculate monthly loan or mortgage payments, total interest paid, and view the full amortization schedule. Enter principal, interest rate, and loan term.
Monthly payment
$1,264.14
Total payment
$455,088.98
Total interest
$255,088.98
127.5% of principal
Payment breakdown
Amortization Schedule
Loans and mortgages enable individuals and businesses to finance major purchases by borrowing capital subject to agreed repayment schedules. Calculating fixed monthly instalments, total interest liabilities, and principal amortisation ensures transparent financial planning and prevents predatory lending surprises.
Fixed-rate installment loans compute the periodic payment ($M$) via the standard annuity amortization formula:
$$M = P \times \frac{r(1 + r)^n}{(1 + r)^n - 1}$$
Where:
| Principal ($P$) | Annual Rate | Term ($n$) | Monthly Payment ($M$) | Total Interest Paid |
|---|---|---|---|---|
| £10,000 | 5.0% | 3 years (36 mos) | £299.71 | £789.52 |
| £25,000 | 7.5% | 5 years (60 mos) | £500.95 | £5,057.06 |
| £250,000 | 4.0% | 25 years (300 mos) | £1,319.59 | £145,876.62 |
In early repayment cycles, the majority of your monthly installment is allocated toward paying accumulated interest. As the outstanding principal gradually declines, the proportion allocated toward interest decreases while the principal repayment accelerates.
JavaScript
function calculateLoan({ principal, annualRatePercent, termYears }) {
const monthlyRate = (annualRatePercent / 100) / 12;
const totalMonths = termYears * 12;
if (monthlyRate === 0) {
const monthlyPayment = principal / totalMonths;
return { monthlyPayment, totalPayment: principal, totalInterest: 0 };
}
const factor = Math.pow(1 + monthlyRate, totalMonths);
const monthlyPayment = principal * (monthlyRate * factor) / (factor - 1);
const totalPayment = monthlyPayment * totalMonths;
const totalInterest = totalPayment - principal;
return {
monthlyPayment: Number(monthlyPayment.toFixed(2)),
totalPayment: Number(totalPayment.toFixed(2)),
totalInterest: Number(totalInterest.toFixed(2)),
};
}
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