Loan Amortization Schedule Calculator | Payment Table

Loan Amortization Schedule

A loan amortization schedule is a table that lists every payment on a loan and splits each one into interest and principal. This calculator builds that table for a fixed-rate loan with equal monthly payments, from three inputs: the loan amount, the annual interest rate, and the term in years.

What the calculator does

Enter the loan amount, the annual interest rate (APR), and the loan term. The calculator returns the monthly payment, the total interest paid over the life of the loan, and the total amount paid. Below those figures it shows the full schedule: one row per month, with the payment, the interest part, the principal part, and the balance still owed after that payment. A copy button exports the whole table as tab-separated text.

The loan amount can be between $1 and $100,000,000. The interest rate can be 0% to 100%. The term can be 1 to 50 whole years. Payments are monthly; other frequencies are not offered.

How amortization works

Amortization means paying a loan down to zero with a fixed, level payment. Each month, interest is charged on the balance still owed. The payment first covers that interest; whatever is left over reduces the balance. Because the balance shrinks every month, the interest charge shrinks too, so a growing share of each payment goes to principal. Early payments are mostly interest. Late payments are mostly principal.

The monthly payment formula

The level payment is sized so the balance reaches exactly zero on the final payment:

M = P × [r(1 + r)ⁿ] / [(1 + r)ⁿ − 1]

• M is the monthly payment.
• P is the principal, the amount borrowed.
• r is the monthly interest rate: the annual rate divided by 100, then by 12.
• n is the number of payments: the term in years times 12.

If the interest rate is 0%, the formula would divide by zero, so the payment is simply the loan amount divided by the number of payments. A $12,000 loan at 0% over 2 years costs $500.00 per month, and every row of its schedule shows $0.00 interest.

For a quick check of the formula: a $10,000 loan at 6% for 1 year has r = 0.06 ÷ 12 = 0.005 and n = 12. Then (1.005)¹² ≈ 1.06168, and M = 10,000 × 0.005 × 1.06168 ÷ 0.06168 ≈ $860.66.

How each row is computed

The interest in a row is the balance carried into that month times the monthly rate. The principal part is the payment minus that interest. The balance after the payment is the old balance minus the principal part. The engine computes each month's balance directly from the loan terms rather than by repeated subtraction, so no rounding error builds up from row to row.

Rounding: why the last payment is different

The table shows whole cents, the way a lender's statement does, and that forces a choice. The calculator uses this convention:

• The payment column shows the level payment rounded to the cent, on every row except the last.
• The interest column is the exact interest for that month, rounded to the cent.
• The principal column is the payment minus the rounded interest, so interest and principal always add up to the payment shown beside them.
• Each balance is the previous balance minus that principal, so the principal column adds up to the loan amount exactly.
• The final row pays off whatever balance remains: its principal is the leftover balance, and its payment is that balance plus the final month's interest.

Because every earlier payment was rounded to whole cents, the leftover balance is rarely an exact payment's worth, so the last payment differs slightly from the others. Real loans work the same way. Total interest and total paid are the sums of the table's columns, not the payment multiplied by the number of months, so the headline figures always match the table beneath them.

Example: $20,000 at 5.5% for 5 years

The monthly rate is 0.055 ÷ 12 ≈ 0.004583 and n = 60. The formula gives a monthly payment of $382.02. The schedule begins:

The first month's interest is $20,000 × 0.055 ÷ 12 = $91.67, leaving $290.35 of the payment for principal. By month 59 the balance is down to $380.49, and the final row clears it:

The last payment is $382.23, 21 cents more than the others. Over the whole loan, total interest is $2,921.41 and the total paid is $22,921.41.

Frequently asked questions

Why is the last payment slightly different?

Every payment is rounded to whole cents, so tiny fractions of a cent accumulate over the loan. The final payment absorbs them by paying off the exact remaining balance plus the last month's interest. In the example above it is $382.23 instead of $382.02.

Is total interest just the monthly payment times the number of months, minus the loan amount?

Almost, but not exactly. That shortcut gives $382.02 × 60 − $20,000 = $2,921.20 for the example loan. The calculator instead sums the cent-rounded interest column, which gives $2,921.41. The difference comes from the rounding of each row and the larger final payment. The summed figure is the one that matches the table.

Why does so much of the first payment go to interest?

Interest is charged on the balance still owed, and the balance is largest at the start. On a $20,000 loan at 5.5%, the first month's interest is $91.67, about a quarter of the $382.02 payment. As the balance falls, the interest charge falls with it, and more of each payment goes to principal.

Can the interest rate be 0%?

Yes. At 0% the payment is the loan amount divided by the number of months, every row shows $0.00 interest, and the balance falls in equal steps.

Does the calculator handle extra payments, fees, or bi-weekly schedules?

No. It models a fixed-rate loan with equal monthly payments and nothing else. Extra payments, origination fees, taxes, insurance, and non-monthly schedules are not included.