Loan Calculator

How to use the loan calculator

1. Enter the loan amount and choose your currency.
2. Enter the annual interest rate your lender quotes, and the term in years (add extra months for terms like 5 years 6 months).
3. Pick a repayment method — equal monthly payment for a standard mortgage or personal loan, equal principal for the style some banks and business loans use.
4. Optionally add an extra monthly payment to see how much interest and time it saves.
5. Review the results, the yearly chart and the full month-by-month schedule. Download CSV opens the schedule in a spreadsheet.

How it works

For the equal-payment method, each instalment is the same and is split between interest and principal:

M = P × i / (1 − (1 + i)^−n)

Each month the interest is the balance multiplied by i, and whatever is left of the payment reduces the balance. As the balance shrinks, the interest portion shrinks and the principal portion grows — that is amortization.

The equal principal method instead repays P ÷ n of the balance every month and adds the interest on top, so the first payment is the largest and each one afterwards is smaller. Because the balance falls faster, total interest is lower for the same term.

Any extra payment is applied to the balance immediately after the scheduled payment. The schedule then ends early, and the last payment is automatically trimmed so you never overpay. The calculator compares that schedule with the same loan without extra payments to show the interest and months saved.

Worked examples

30-year mortgage. Borrow $200,000 at 6% for 30 years. The payment is $1,199.10 a month, total interest is $231,676.38 and you repay $431,676.38 in all. The very first payment contains $1,000 of interest and only $199.10 of principal.

Adding $200 a month. The same loan with $200 extra each month is paid off in 21 years instead of 30 — 108 months early — and interest falls to $151,875.87, a saving of $79,800.51.

Car loan. $25,000 at 4.5% over 5 years costs $466.08 a month and $2,964.53 in interest, for a total of $27,964.53.

Equal principal versus equal payment. On $100,000 at 6% for 10 years, equal payment costs $1,110.21 every month and $33,224.60 in interest. Equal principal starts at $1,333.33, ends at $837.50, and costs $30,250 — about $2,975 less, in exchange for higher payments early on.

Reading the amortization schedule

Each row of the table is one month. Payment is the scheduled instalment, split into Principal (the part that reduces your debt) and Interest (the lender’s charge for that month). Extra is anything you add voluntarily, and Balance is what remains afterwards.

Two patterns are worth spotting. First, the crossover month — the point where more of your payment goes to principal than to interest. On a 30-year loan at 6% that happens in month 223, which is why paying it down early matters so much. Second, the size of the last row: if it is much smaller than the others, your loan finishes with a partial payment, which is normal whenever extra payments or rounding are involved. The yearly chart above the table shows the same information grouped into years, so you can see the interest bar shrinking as the principal bar grows.

Tips and common mistakes

• Compare APR, not just the rate. APR folds arrangement fees into the quoted rate, so two loans at the same nominal rate can cost different amounts.
• Shortening the term beats overpaying at the end. Extra payments in the first years remove the most interest, because the balance they attack is largest.
• Check for early repayment penalties. Some fixed-rate loans charge a fee for overpaying; enter the fee separately when comparing.
• Watch the payment frequency. Bi-weekly plans make 26 half payments a year, the equivalent of 13 monthly payments — that alone shortens a 30-year mortgage by roughly four to six years.
• Rounding differs by lender. Banks usually round each instalment to the cent and adjust the final payment, so your statement may differ from this schedule by a few cents.

These results are estimates for planning and comparison; they are not an offer of credit or financial advice.

Glossary

• Principal – the outstanding amount you still owe.
• Amortization – repaying a loan through instalments that cover interest and principal.
• Term – the total length of the loan, in years or months.
• Payoff time – how long it actually takes to reach a zero balance, including extra payments.
• Balloon payment – a large final payment used by some loans instead of full amortization.

Last reviewed: September 21, 2026