Calculate your monthly loan repayment, total interest, and total cost for any personal loan, car loan, or credit agreement using our free online loan calculator.
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Formula: M = P [ r(1+r)^n ] / [ (1+r)^n - 1 ] where r = monthly rate, n = number of months
Common Loan Payment Examples
| Loan Amount | Interest Rate | Term | Monthly Payment | Total Interest |
|---|---|---|---|---|
| $5,000 | 7.5% | 24 months | $225.12 | $402.88 |
| $10,000 | 7.5% | 36 months | $311.06 | $1,197.96 |
| $10,000 | 7.5% | 60 months | $200.38 | $2,022.74 |
| $20,000 | 9.0% | 48 months | $497.70 | $3,889.60 |
| $25,000 | 6.0% | 60 months | $483.32 | $3,998.88 |
How It Works: Understanding Loan Amortisation
A loan calculator uses the standard amortisation formula to determine your fixed monthly repayment. Like a mortgage, a personal loan or car loan is amortised — meaning each monthly payment covers both a portion of the original principal and the interest that has accrued on the outstanding balance. In the early months of a loan, a larger share of each payment goes toward interest. As the balance reduces, more of each payment goes toward paying down the principal.
The formula is: M = P [ r(1+r)^n ] / [ (1+r)^n - 1 ], where M is the monthly payment, P is the loan principal, r is the monthly interest rate (the annual rate divided by 12), and n is the total number of monthly payments. For example, a $10,000 loan at 7.5% annual interest over 36 months produces a monthly payment of $311.06. Over the life of the loan, you would pay $11,197.96 in total — meaning $1,197.96 in interest.
Loan Term vs. Interest Rate: What Matters More?
Both the interest rate and the loan term have a significant impact on the total cost of a loan, but they work in opposite ways. A lower interest rate directly reduces the amount of interest charged on the outstanding balance each month, which lowers both the monthly payment and the total cost. A shorter loan term means you pay off the balance faster, which also reduces the total interest paid — but it increases the monthly payment because the principal is spread over fewer instalments.
The key insight is that extending a loan term to reduce monthly payments always increases the total amount you pay. For example, a $10,000 loan at 7.5% costs $1,197.96 in interest over 36 months, but $2,022.74 in interest over 60 months. If you can afford the higher monthly payment, choosing a shorter term will save you money in the long run.
Historical Context: A Brief History of Consumer Lending
The concept of lending money at interest is one of the oldest financial practices in human history, with records of interest-bearing loans dating back to ancient Mesopotamia around 3000 BCE. The Code of Hammurabi (c. 1754 BCE) even set legal limits on interest rates — 33.3% per year for grain loans and 20% for silver loans — making it one of the earliest examples of consumer protection legislation.
Modern consumer lending as we know it — with fixed monthly instalments, standardised interest rates, and formal credit agreements — largely developed in the United States during the early 20th century. The rise of the automobile industry in the 1910s and 1920s created a mass market for instalment credit, as most consumers could not afford to pay for a car outright. General Motors Acceptance Corporation (GMAC), founded in 1919, was one of the first large-scale consumer finance companies, pioneering the model of fixed monthly car loan payments that is still used worldwide today.
Frequently Asked Questions
What is the difference between a personal loan and a mortgage?
Both are amortising loans that use the same repayment formula, but they differ in purpose, size, and term. A mortgage is secured against a property, which allows lenders to offer much lower interest rates and longer terms (15–30 years). A personal loan is typically unsecured, meaning no collateral is required, but this results in higher interest rates and shorter terms (1–7 years). This loan calculator is designed for personal loans, car loans, and similar shorter-term credit agreements.
What is APR and how does it differ from the interest rate?
The interest rate is the annual cost of borrowing the principal, expressed as a percentage. The Annual Percentage Rate (APR) is a broader measure that includes the interest rate plus any additional fees and charges (such as origination fees or arrangement fees), expressed as a single annual figure. When comparing loan offers, always compare APRs rather than headline interest rates, as the APR gives a more accurate picture of the true cost of borrowing.
Can I pay off my loan early?
Most lenders allow early repayment, but some charge an early repayment fee (also called a prepayment penalty) to compensate for the interest they will no longer receive. Before making an overpayment or settling a loan early, check your loan agreement for any early repayment charges. In many cases, even with a small fee, paying off a loan early will save you money on the total interest paid.