Online Loan Amortization Schedule Calculator

An online loan amortization schedule calculator estimates your fixed monthly payment and total interest, then shows how each payment is divided between principal and interest over the loan term. Enter the loan amount, annual percentage rate (APR), and term to see a schedule based on monthly payments.

Formula

This calculator uses the standard fixed-payment amortizing-loan formula. Let P be the amount borrowed in dollars, APR the annual percentage rate expressed as a percentage, r the monthly interest rate as a decimal, and n the total number of monthly payments. The formulas are:

• Monthly rate: r = APR ÷ 1200.
• Number of payments: n = 12 × term in years.
• Monthly payment: M = P × r ÷ [1 − (1 + r)⁻ⁿ].
• Total interest: I = M × n − P, using the displayed payment rounded to cents.

The schedule is calculated month by month. For each period, interest is the opening balance multiplied by r; principal repaid is the payment minus that interest; and the closing balance is the opening balance minus principal repaid. In symbols, interest_k = balance_k−1 × r, principal_k = M − interest_k, and balance_k = balance_k−1 − principal_k. All money amounts are in dollars, rates are annual percentages unless labeled monthly, and the payment count is in months.

Worked Example

Using the calculator’s defaults—$20,000 borrowed, 8% APR, and a five-year term—the monthly rate is 8 ÷ 1200 = 0.0066667, and the term is 5 × 12 = 60 payments.

1. Substitute into the payment formula: $20,000 × 0.0066667 ÷ [1 − (1 + 0.0066667)⁻⁶⁰].
2. The unrounded monthly payment is about $405.528; rounded to cents, it is $405.53.
3. Total of the 60 displayed monthly payments: $405.53 × 60 = $24,331.80.
4. Estimated total interest: $24,331.80 − $20,000 = $4,331.80.

For the first month, interest is $20,000 × 0.0066667, or about $133.33. The $405.53 payment therefore reduces principal by about $272.20, leaving an estimated balance of $19,727.80. Later interest charges generally decline as the balance falls, so more of each level payment goes toward principal. The final payment may differ slightly because of rounding or lender-specific calculation practices.

Assumptions

• The interest rate stays fixed for the full term.
• Payments are equal and made monthly at the end of each period.
• Interest accrues monthly at APR divided by 12.
• Fees, taxes, insurance, private mortgage insurance, escrow, late charges, and extra payments are not included.

How to Read an Amortization Schedule

An amortization schedule is a dated or numbered list of payments that tracks how a loan balance is repaid. A typical row shows the payment, the interest portion, the principal portion, and the remaining balance. The calculator’s headline payment is the estimated regular installment; its total-interest figure is the sum of scheduled payments minus the original principal under the stated assumptions.

Early in a fully amortizing loan, the balance is relatively high, so the interest portion of a level payment is larger. As principal is paid down, interest is calculated on a smaller balance and the principal portion grows. This does not mean the lender charges a larger interest rate at the start: with a fixed rate, the changing split results from the declining balance.

When to Use It and What It Leaves Out

Use an online amortization schedule to understand the arithmetic of a fixed-rate loan, inspect how the balance changes, or compare a lender’s disclosed payment schedule with a simplified estimate. Enter the principal actually financed, rather than an asset’s price if a down payment or trade-in reduces the amount borrowed. Use the APR shown in the loan documents when available; the example rate is only an editable illustration, not a statement about rates available to borrowers.

This calculator does not produce a lender’s official payoff amount. Actual schedules can be affected by payment dates, daily interest calculations, fees added to the balance, changing rates, skipped or late payments, and rounding conventions. An adjustable-rate loan cannot be represented accurately by one fixed APR for its entire term. A loan with a final balloon payment, interest-only period, or irregular payment plan also needs a different calculation.

Common Errors and Alternatives

• Confusing APR and monthly rate: enter annual APR as a percentage, such as 8, not 0.08 or 8 per month. The formula converts it to a monthly decimal.
• Using the wrong principal: the amount borrowed may differ from a purchase price. Include only amounts that are actually financed, and account for financed charges if the lender includes them.
• Expecting exact cents throughout: displayed payments are rounded to cents, while lenders may calculate interest using more precise balances or different timing. Small differences can accumulate.
• Assuming extra payments are automatic: additional principal payments can change the payoff date and interest, but this calculator does not model them. A separate extra-payment calculation needs the amount and timing of those payments.

A full schedule can be built by repeating the monthly balance steps for every payment. For loans with fees, variable rates, or nonmonthly payments, use the lender’s disclosed schedule or a calculator that includes those specific inputs. The arithmetic here is useful for understanding principal, interest, and balance, but it cannot predict approval, the lender’s final terms, or the exact payoff on a particular date.

Frequently Asked Questions

What is an online loan amortization schedule?
It is a web-based estimate showing each scheduled payment’s interest and principal portions and the remaining loan balance. The result depends on the loan amount, rate, term, payment timing, and assumptions used by the calculator.

Does an amortization schedule show the total interest?
Yes, a standard schedule can show total interest by adding the scheduled payments and subtracting the original principal. This calculator uses its monthly payment rounded to cents for that total.

Why does more of each payment go to principal later?
With a fixed rate, monthly interest is based on the outstanding balance. As the balance declines, less interest accrues, leaving more of the same payment to reduce principal.

Can I use this schedule for an adjustable-rate loan?
Only as a simplified estimate for a period when the rate is known and unchanged. A schedule using one APR will not account for future rate adjustments.

Why is my lender’s payment different?
The financed amount, rate, payment dates, fees, rounding, or interest-accrual method may differ from the calculator’s assumptions. Check the loan disclosure for the figures and method used for your account.

This result is an estimate for educational purposes, and the lender’s disclosure gives the exact figures.

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in p | Loan amount | $ | 20000 | 1 | 100000000
in apr | Interest rate (APR) | % | 8 | 0.01 | 100
in yrs | Loan term | years | 5 | 0.0833 | 50
out pmt | Monthly payment | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2