How to Calculate Your Loan Payment and Total Interest

To calculate a loan payment, enter the loan amount, annual interest rate and term, and the calculator returns your fixed monthly payment, the total interest you'll pay and the full amount repaid over the life of the loan. The ByteTools Loan Calculator does this for any fixed-rate loan — personal, auto, student or installment — and shows a month-by-month amortization schedule, all computed privately in your browser.

What the calculator does

A loan calculator answers the questions that actually matter before you borrow: what will I pay each month, how much interest will this cost me in total, and how does the balance shrink over time? Enter three numbers and you get all three answers instantly:

• Monthly payment — the fixed amount due each period.
• Total interest — the extra you pay on top of the amount borrowed.
• Total cost — principal plus interest over the whole term.

It also expands into a full amortization schedule, breaking every payment into its interest and principal parts so you can watch the balance fall. It handles a 0% rate, terms in years or months, and any currency symbol.

Step by step

Using it takes under a minute:

1. Pick your currency and enter the loan amount — the principal you're borrowing, for example 20,000.
2. Enter the annual interest rate as a percentage, such as 7.5. The calculator converts it to a monthly rate for you.
3. Enter the term and choose years or months — say 5 years.
4. Read the results: the monthly payment, total interest and total paid appear immediately.
5. Expand the amortization schedule to see every payment's interest/principal split and the running balance.

A worked example

Suppose you borrow 20,000 at 7.5% annual interest over 5 years (60 monthly payments). The calculator applies the standard amortization formula and returns roughly a 401 monthly payment. Over the full term you'd pay about 4,046 in interest, for a total cost near 24,046.

Input	Value
Loan amount	20,000
Annual rate	7.5%
Term	5 years (60 months)
Monthly payment	~401
Total interest	~4,046
Total repaid	~24,046

The amortization schedule shows why the split shifts over time: the first payment is mostly interest (charged on the full 20,000), while the last is almost all principal, because interest is always calculated on the shrinking balance.

The math behind it

Fixed-rate loans use the amortization formula M = P × r × (1 + r)^n / ((1 + r)^n − 1), where P is the amount borrowed, r is the monthly rate (annual rate ÷ 12) and n is the number of payments. Each payment M is identical, but the interest portion falls and the principal portion rises every month. You don't need to compute this by hand — the calculator does it — but knowing the formula explains why extra early payments save so much: they cut the balance that all future interest is charged on.

Private and free in your browser

Every calculation runs entirely in your browser. Your loan amount, rate and schedule are never uploaded to a server, so your finances stay completely private — useful when you're comparing offers you'd rather not share. Note the results use the nominal interest rate and exclude fees, insurance and origination charges, so a lender's APR may make the real cost slightly higher. Treat the numbers as planning estimates, not financial advice.

Try the Loan Calculator — free and 100% in your browser.

FAQ

What three numbers do I need to calculate a loan payment?

The loan amount (principal), the annual interest rate, and the term. With those, the calculator produces the monthly payment, total interest and total cost, plus a full amortization schedule.

Can I use it for auto and student loans?

Yes. It works for any fixed-rate installment loan — personal, auto, student or otherwise. Enter the amount, rate and term for that loan and the results apply directly.

Does the result include APR and fees?

No. It uses the nominal interest rate on the amount borrowed and excludes origination fees, insurance and other charges. Your lender's APR folds those in, so the true cost may be a little higher than shown.

How can I lower the total interest I pay?

A shorter term, a lower rate, or extra payments toward principal all reduce total interest. Overpaying early has the biggest effect because it shrinks the balance that future interest is charged on.

Are my loan figures kept private?

Yes. Everything is computed locally in your browser and never sent to a server, so your amount, rate and amortization schedule never leave your device.

Related free tools

• EMI Calculator — equated monthly installments for any loan.
• Mortgage Calculator — payments and interest for home loans.
• Simple Interest Calculator — quick non-compounding interest.
• Debt Payoff Calculator — plan how fast to clear balances.

Built by ByteVancer

ByteTools is a free product of ByteVancer, a software and web development studio building web apps, SaaS and custom software. If you need custom financial calculators or fintech features built for your product, explore how ByteVancer can help.