Finance Amortization Table Calculator and Guide

A finance amortization table shows each scheduled loan payment split between principal and interest, along with the balance left afterward. Enter a loan amount, annual APR, and term to calculate the monthly payment and total interest; the calculator uses those inputs to describe the payment schedule mathematically.

Formula

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

M = P × r / [1 − (1 + r)⁻ⁿ]

• M is the monthly payment in dollars, rounded to the nearest cent.
• P is the starting principal, or loan amount, in dollars.
• r is the monthly interest rate as a decimal: annual APR ÷ 1,200. For an 8% APR, r = 0.08 ÷ 12.
• n is the number of monthly payments: years × 12.

The total-interest estimate is I = M × n − P, using the rounded monthly payment shown above. The calculator reports the regular payment and aggregate interest; it does not print a row for every month. An amortization table is built by repeating the same balance calculation for each payment period.

Worked Example

Using the calculator’s default inputs—$20,000 principal, 8% APR, and a 5-year term:

1. Convert the APR to a monthly decimal rate: 8 ÷ 1,200 = 0.0066667.
2. Convert the term to payments: 5 × 12 = 60 months.
3. Apply the payment formula: $20,000 × 0.0066667 ÷ [1 − (1 + 0.0066667)⁻⁶⁰] = $405.53 per month, rounded to cents.
4. Calculate total interest using the rounded payment: $405.53 × 60 − $20,000 = $4,331.80.

Thus, the estimate is a monthly payment of $405.53 and total interest of $4,331.80, assuming the same payment and rate throughout.

Assumptions

• The interest rate is fixed for the entire term.
• Payments are made monthly at the end of each period.
• Interest accrues monthly at APR ÷ 12.
• There are no fees, taxes, insurance, PMI, escrow charges, or other amounts added to the payment.

How a Finance Amortization Table Works

Each row in a standard amortization table represents one scheduled payment period. The interest portion is calculated from the balance outstanding at the beginning of that period. The remainder of the payment reduces principal. Since the balance generally falls over time, the interest portion tends to shrink and the principal portion tends to grow, even though the scheduled payment stays level.

For a monthly schedule, the core row calculations are:

• Interest for the month = opening balance × monthly rate.
• Principal repaid = scheduled payment − interest for the month.
• Closing balance = opening balance − principal repaid.

For example, on the first month of the default example, interest is about $133.33 ($20,000 × 0.0066667). Subtracting that from the $405.53 payment leaves about $272.20 to reduce principal, so the balance falls to roughly $19,727.80. Later rows calculate interest from the new, lower balance. Small differences can appear if a table rounds interest and balances each month; the final payment may need a minor adjustment to bring the balance exactly to zero.

When to Use the Table and How to Read It

An amortization schedule can help explain the timing of repayment, estimate a remaining balance after a given number of payments, and separate principal repayment from interest cost. It can be useful for comparing scenarios by changing the loan amount, APR, or term, while keeping in mind that the calculator compares only the figures entered—not lender-specific offers or product terms.

Look for the payment number or date, opening balance, payment, interest, principal, and closing balance. The first rows reveal how the initial payment is divided. The last rows show how little principal remains and how the loan reaches its scheduled end. Total interest is the sum of the interest column, not the sum of all payments; total payments also include repayment of the original principal.

Common Mistakes and Limits

• Mixing APR and monthly rates: An annual percentage such as 8% must be converted to a monthly decimal for this formula by dividing by 1,200. Entering 8 as the monthly rate would be a unit error.
• Confusing principal with total cost: The loan amount is not the total paid. Scheduled payments cover both principal and interest, while fees or optional products may add costs outside this estimate.
• Expecting every real loan to follow the schedule: Variable rates, skipped or late payments, fees, payment-date conventions, and extra principal payments can change the actual schedule.
• Rounding each line differently: Calculators may retain extra precision internally, while statements round posted amounts to cents. A final row can differ slightly as a result.

This standard formula models a fully amortizing loan with a positive APR and equal monthly payments. It is not a substitute for a lender’s payment schedule, and the result may differ when the loan has an introductory rate, irregular payment timing, a balloon payment, or other contractual features. Use the APR and term supplied for the specific loan rather than treating the example values as market information.

Frequently Asked Questions

What does an amortization table show?
It lists scheduled payments and shows how much of each payment goes to interest and principal, plus the balance remaining after each payment.

How do I calculate an amortization payment?
Convert the annual APR to a monthly decimal rate, multiply the term in years by 12, and use the fixed-payment formula shown above. Round the resulting payment to cents.

Why is more of the early payment interest?
Interest is calculated on the outstanding balance. That balance is largest near the beginning, so the interest charge takes a larger share of a level payment. As principal falls, the interest share generally declines.

Does this calculator create a month-by-month table?
No. It calculates the level monthly payment and total interest. A full table requires repeating the interest, principal, and balance calculations for every payment period.

Does an extra payment change an amortization schedule?
Usually, an extra amount applied to principal reduces the balance and can change later interest and payoff timing. This calculator assumes only the scheduled level payments, so it does not model extra payments.

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

Related

• Auto Loan Amortization Table Calculator and Guide
• Amortization Table Annual Payments Calculator
• Amortization Table Calculator and Accounting Explained

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