Loan Amortization Table Calculator and Payment Schedule

A loan amortization table calculator estimates a fixed monthly payment and shows how each payment is divided between interest and principal over the loan term. Enter the loan amount, annual percentage rate (APR), and term to see the payment and total interest; the schedule itself can be generated from those same figures using the monthly balance formula.

Formula

The calculator uses the standard level-payment formula for a fully amortizing loan: M = P × r ÷ [1 − (1 + r)⁻ⁿ]. Here, M is the monthly payment in dollars, P is the starting principal in dollars, r is the monthly interest rate as a decimal, and n is the total number of monthly payments. Convert the APR from a percent per year to a monthly decimal with r = APR ÷ 1,200; convert the term in years to months with n = 12 × years.

Total interest is calculated as I = M × n − P, where I is total interest in dollars. The payment is rounded to cents for display, and the total uses that displayed payment multiplied by the number of months. A row-by-row schedule can then be calculated as follows: each month’s interest is the balance at the start of that month multiplied by r; principal paid is the payment minus that interest; and the ending balance is the starting balance minus principal paid.

Worked Example

Using the calculator’s default inputs: principal P = $20,000, APR = 8%, and term = 5 years:

1. Monthly rate: r = 8 ÷ 1,200 = 0.0066667, or about 0.66667% per month.
2. Number of payments: n = 5 × 12 = 60.
3. Monthly payment: M = 20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰] = $405.53 when rounded to cents.
4. Total of the rounded payments: $405.53 × 60 = $24,331.80.
5. Total interest: $24,331.80 − $20,000 = $4,331.80.

For the first schedule row, interest is $20,000 × 0.0066667, or about $133.33. Subtracting that from the $405.53 payment gives about $272.20 toward principal, leaving an estimated balance of $19,727.80. Later rows use each new balance, so the interest portion generally declines while the principal portion rises. Small differences can appear in a detailed schedule because the lender may calculate and round interest by day or apply payments on particular dates.

Assumptions

• The APR and scheduled payment remain fixed throughout the term.
• Payments are made monthly, with the first payment one month after the loan begins.
• Interest compounds monthly at APR divided by 12.
• The estimate excludes fees, taxes, insurance, PMI, and escrow; none of these are calculator inputs.
• The full scheduled payment is applied to principal and interest, and the loan is paid as scheduled with no missed or extra payments.

How to Read an Amortization Table

An amortization table lists the payment period, beginning balance, scheduled payment, interest, principal, and ending balance. In a conventional fixed-rate, fully amortizing loan, the scheduled payment stays level, but its components change. Interest is calculated on the remaining balance, so a larger share of early payments can go to interest. As principal falls, the interest charged in later periods falls too, allowing more of the same payment to reduce principal.

The first payment is not the only useful row. The ending balance after a chosen number of payments estimates how much principal remains at that point. It does not necessarily equal a payoff quote: a payoff figure can account for accrued interest through a specific date and other amounts not included in this calculation. Likewise, the total interest assumes every scheduled payment is made on time and unchanged.

When to Use It and What It Does Not Show

Use an amortization estimate to understand the payment pattern for a loan with a fixed rate and regular monthly installments, or to check how principal and interest contribute to the scheduled payment. It can help explain quoted loan figures, but it cannot reproduce a lender’s full statement unless the lender’s calculation conventions and all charges are represented.

This calculator does not create the full table as an output; it calculates the level payment and total interest from the selected inputs. To build the table, repeat the monthly row calculations from the formula section, using the previous ending balance as the next beginning balance. For an adjustable rate, irregular payment dates, a balloon payment, interest-only period, or changing payment amount, a single fixed-rate formula is not enough to model the entire contract.

Common Errors and Useful Comparisons

• Mixing annual and monthly units: enter APR as an annual percentage, such as 8, not as 0.08 or as a monthly rate. The formula converts it to a monthly decimal.
• Using years where months are required: a five-year term means 60 monthly payments, not five.
• Confusing payment with total borrowing cost: the monthly payment covers principal and interest in this model. Total interest is the sum of interest over the assumed schedule, not the loan’s total repayment.
• Expecting an exact statement balance: payment dates, daily interest calculations, rounding, fees, and extra payments can make an actual balance differ.

A shorter term generally means fewer scheduled payments and less time for interest to accrue, but the formula also produces a different monthly payment. Comparing two estimates is meaningful only when you use accurate principal, APR, and term figures and understand whether the same costs are included. Get actual rates and charges from the lender rather than treating an example input as a quoted offer.

Frequently Asked Questions

What does a loan amortization table show?
It shows each scheduled payment’s interest and principal portions and the remaining balance after the payment, under the assumptions used to calculate it.

How do I calculate the interest in one monthly payment?
Multiply the beginning balance for that month by the monthly rate. For an 8% APR under monthly compounding, the rate used in the estimate is 8 ÷ 1,200 per month.

Why does the principal portion increase over time?
With a fixed rate and level payment, interest is charged on the remaining balance. As principal is repaid, the balance and its interest charge fall, leaving more of the payment for principal.

Does this calculator include extra payments or fees?
No. It assumes regular level payments and excludes extra principal payments and charges. Those amounts can change the payoff date, total interest, or balance.

Why is my lender’s payment or balance slightly different?
The lender may use different rounding, payment dates, day-count conventions, fees, or a rate structure not represented here. Check the loan disclosure and servicing figures for the contract-specific amounts.

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

Related

• Auto Loan Amortization Table Excel Calculator
• Amortization Table With Variable Payments: Calculator
• Loan Amortization Table Calculator and Guide

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