Standard Amortization Table Calculator and Guide

A standard amortization table shows how each scheduled loan payment is divided between interest and principal, along with the balance remaining after each payment. Enter a loan amount, annual APR, and term to calculate a level monthly payment and total interest; the figures assume regular monthly payments and a fixed rate.

Formula

For a fixed-rate loan with equal monthly payments, the payment is calculated as:

M = P × r ÷ [1 − (1 + r)−n]

• P is the original loan principal, in dollars.
• APR is the annual percentage rate entered as a percentage; the monthly rate is r = APR ÷ 1200.
• n is the total number of monthly payments, calculated as years × 12.
• M is the monthly payment, in dollars, rounded to the nearest cent.

Total interest in this calculator is M × n − P. It uses the rounded monthly payment, so it reflects the repeated scheduled payment shown in the result. A real final payment can differ slightly if the lender adjusts for rounding, payment dates, or account-specific terms.

Worked Example

With the default inputs, the principal is $20,000, APR is 8%, and the term is 5 years. The monthly rate is 8 ÷ 1200 = 0.0066667, and the number of payments is 5 × 12 = 60.

Substitute those values into the payment formula:

M = 20,000 × 0.0066667 ÷ [1 − (1.0066667)−60]

The unrounded result is about $405.53, so the monthly payment rounded to cents is $405.53. Total interest using the displayed payment is 60 × $405.53 − $20,000 = $4,331.80.

Assumptions

• The interest rate remains fixed for the full term.
• Payments are equal, made monthly, and treated as occurring at the end of each monthly period.
• Interest accrues monthly using APR divided by 12.
• The calculation excludes fees, taxes, insurance, mortgage insurance, escrow, and any additional or missed payments.

What a Standard Amortization Table Shows

A full table typically has one row for each payment period. Its columns commonly include the payment number or date, opening balance, scheduled payment, interest portion, principal portion, and closing balance. The opening balance of the first row is the amount borrowed. Each later row begins with the previous row’s closing balance.

For a monthly schedule, interest for a period is generally calculated from the balance at the start of that period and the monthly rate. The principal portion is the payment minus that period’s interest. The new balance is the opening balance minus principal repaid. Early in a level-payment loan, the outstanding balance is relatively high, so interest takes a larger share of the payment. As principal falls, the interest portion usually declines and the principal portion increases.

This calculator returns the payment and total interest rather than listing all rows. A table can be generated by repeating the period-by-period calculation. For example, at the default values, the first month’s interest is approximately $133.33 ($20,000 × 0.08 ÷ 12); the rest of the $405.53 payment, approximately $272.20, reduces principal.

How to Read and Use the Results

The monthly payment is the scheduled loan payment under the stated assumptions, not necessarily the entire amount due on a bill. For a mortgage, for instance, taxes or insurance may be billed alongside principal and interest, but they are not part of this formula. Check the loan documents for the actual payment structure and any charges included in the amount due.

Total interest estimates the interest paid across all scheduled payments when the rounded payment is made for the full term. It does not include the original principal, so it should not be confused with total payments. In the example, total scheduled payments are 60 × $405.53 = $24,331.80; subtracting $20,000 of principal leaves $4,331.80 in estimated interest.

To use the calculator meaningfully, enter the amount actually financed, the annual APR stated for the loan, and the number of years in the repayment term. If a lender quotes a monthly rate rather than an annual APR, do not enter it as though it were an annual percentage. Obtain the applicable figures from the lender’s disclosure rather than assuming a rate or term.

Limits and Common Misunderstandings

“Standard amortization” describes a common level-payment structure, not every loan. The result may not represent a variable-rate loan, an interest-only period, a balloon payment, irregular payment dates, or a loan with changing installments. An adjustable rate can change the amount of interest and may require a later payment recalculation.

• APR is not always the rate used to accrue interest. This estimate treats APR as a nominal annual rate divided by 12. Loan disclosures may distinguish an interest rate from APR, which can reflect other borrowing costs.
• Rounding affects the last cents. The calculator rounds the payment to cents and uses that amount for total interest. A lender’s system may calculate daily interest or make a small adjustment to the final payment.
• Extra payments change the schedule. Additional principal payments can reduce the balance and future interest, but their timing and application matter. They are not included here.
• Fees and add-ons are outside the calculation. A financed fee changes the principal; a separately paid charge does not. Taxes, insurance, and escrow are not inferred from the loan amount.

The formula is useful for understanding a fixed-payment pattern, but it cannot reproduce a lender’s complete account ledger without the contract’s rate method, dates, rounding rules, fees, and payment history.

Frequently Asked Questions

What is a standard amortization table?
A standard amortization table lays out scheduled loan payments over time and shows how much of each payment goes to interest and principal, plus the remaining balance.

Does an amortization table show the total amount paid?
A complete table lists payments period by period. Adding them gives total scheduled payments; subtracting the original principal gives estimated interest when there are no extra charges or payment changes.

Why does more of my early payment go to interest?
Interest is calculated on the outstanding balance. At the beginning, the balance is largest, so the interest portion is larger; as principal is repaid, the balance and subsequent interest generally fall.

Does this calculator include taxes or insurance?
No. It estimates principal-and-interest payments only. Taxes, insurance, mortgage insurance, escrow, fees, and other charges require separate figures.

Can I use this for a variable-rate loan?
Only as a simplified estimate for a period when a particular rate applies. If the rate changes, the payment allocation and possibly the scheduled payment can change too.

Why might my lender’s schedule differ by a few cents?
Daily interest, payment dates, rounding conventions, payment posting, fees, and final-payment adjustments can produce differences from a monthly textbook estimate.

This result is an estimate, 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 | $ | round(p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)), 2) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2