Interest calculators help you see exactly what a loan costs and why. Use them to compare the two ways interest is charged, flat rate and reducing balance, build a full repayment schedule, check how much paying early would save, and find the true yearly rate after fees. Every tool here works for more than 70 currencies and shows clear, lender neutral results, so you can plan with confidence wherever you are.
Our interest calculators
Pick the tool that matches what you want to work out:
Flat Rate Loan Calculator
See the payment when interest is charged on the full original amount for the whole term.
Reducing Balance Calculator
See the payment when interest is charged only on the balance you still owe, so it falls over time.
Amortization Schedule
Get a full month by month breakdown of how each payment splits between interest and principal.
Loan Prepayment Calculator
See how much extra payments save you in total interest and how many months they cut from your loan.
Effective Interest Rate Calculator
Find the true yearly cost of a loan after compounding and fees, so you can compare offers fairly.
What is loan interest?
Interest is the cost of borrowing money, shown as a yearly percentage of the amount you owe. Two loans with the same rate can still cost very different amounts, because what matters is how the interest is charged and for how long. The calculators above let you test each part so there are no surprises.
Flat rate vs reducing balance
This is the single most important idea in loan interest, and it is where most people overpay.
- Reducing balance. Interest is charged each month on the balance you still owe. As you repay, the balance falls, so the interest falls too. Most banks use this method.
- Flat rate. Interest is charged on the full original amount for the whole term, even though your balance is going down. This always costs more than it first appears.
As a rule of thumb, a 5% flat rate is close to about a 9.8% reducing balance rate over 5 years, almost double. Always ask which method a lender uses, then compare like with like. Try the flat rate calculator and the reducing balance calculator side by side to see the gap.
What is an amortization schedule?
An amortization schedule is a table that shows every payment over the life of a loan, split into how much goes to interest and how much clears the balance. On most loans the early payments are mostly interest, and the later ones mostly principal. Seeing this helps you understand why paying extra early saves so much. Build one with the amortization schedule tool.
How prepayment cuts your interest
Paying more than your scheduled amount, or making a one time lump sum, reduces the balance that interest is charged on. On long loans even small extra payments early on can save a large amount and shorten the term by months or years. The loan prepayment calculator shows your exact saving, but always check your agreement for any early payment fee first.
Effective interest rate and APR: the true cost
The rate a lender advertises is not always the true cost. The effective interest rate accounts for how often interest is added during the year, and the APR also folds in fees such as an origination or processing charge. Comparing the effective rate or APR, rather than the headline rate, is the only fair way to judge two offers. Work it out with the effective interest rate calculator.
Which calculator should you use?
- Comparing two loan quotes? Use the effective interest rate calculator to compare the true cost.
- A dealer or lender quoted a flat rate? Use the flat rate calculator, then the reducing balance one, to see the real difference.
- Want to see your full repayment plan? Use the amortization schedule.
- Thinking about paying extra? Use the loan prepayment calculator to see the saving.
- Just want your monthly payment? Use the main loan calculator on the home page.
Frequently asked questions
What is the difference between flat rate and reducing balance interest?
Reducing balance charges interest only on the balance you still owe, so it falls as you repay. Flat rate charges interest on the full original amount for the whole term, which costs more. A 5% flat rate is close to about 9.8% on a reducing balance basis over 5 years.
What is an effective interest rate?
The effective interest rate is the true yearly rate once you account for how often interest is added during the year. The APR goes further and includes fees, so it is the fairest way to compare two loan offers.
What is an amortization schedule?
It is a table showing every payment over the life of a loan, split into interest and principal. Early payments are mostly interest, and later ones mostly clear the balance.
Does paying my loan early save money?
Usually yes. Extra payments reduce the balance that interest is charged on, which lowers your total interest and can shorten the loan. Check your agreement for any early payment fee first.
Do these calculators work for any currency?
Yes. Every tool supports more than 70 currencies. The interest math is the same everywhere, only the currency label changes.
Built and maintained by Hira Fatima, BSc in Computer Science (BSCS)
Hira builds, tests, and maintains the calculators on loancalc.io and writes the guides that go with them.
How we calculate: Reducing balance uses the standard EMI formula; flat rate charges interest on the full original amount. | Last updated: June 2026
Disclaimer: This calculator gives estimates for planning only and is not financial advice. Your actual figures may differ due to fees, taxes, and lender policies. Confirm with your bank or lender before you borrow.