Personal Loan Calculator With Amortization Table

A personal loan calculator with an amortization table estimates your monthly payment, total interest, and remaining balance as you repay a fixed-rate loan. Enter the loan amount, annual percentage rate (APR), and term to see the payment calculation; a full month-by-month table can then show how each payment is split between interest and principal.

Formula

The calculator uses the fixed-payment loan formula. It calculates the monthly payment from the principal, monthly interest rate, and number of monthly payments:

Payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the amount borrowed, in dollars.
• r is the monthly interest rate as a decimal: APR ÷ 1,200. For an 8% APR, r = 0.08 ÷ 12.
• n is the number of monthly payments: loan term in years × 12.

Total interest is estimated as the monthly payment multiplied by the number of payments, minus the original principal: Total interest = payment × n − P. The payment is rounded to cents before the total is calculated, so the displayed interest follows the calculator’s rounded-payment convention.

Worked Example

Using the default inputs—$20,000 borrowed, 8% APR, and a five-year term—the monthly rate is 0.08 ÷ 12 = 0.0066667, and the term is 5 × 12 = 60 months.

Payment = 20,000 × 0.0066667 ÷ [1 − (1 + 0.0066667)⁻⁶⁰] = $405.53 per month, rounded to the nearest cent.

Total interest = ($405.53 × 60) − $20,000 = $4,331.80. The calculation therefore estimates 60 payments of $405.53 and $4,331.80 in interest. Actual final payments can differ if a lender uses different payment dates, rounding, or loan terms.

Assumptions

• The interest rate remains fixed throughout the term.
• Payments are equal monthly payments made at the end of each monthly period.
• Interest is modelled monthly at APR ÷ 12.
• Fees, taxes, insurance, and other charges are not included.

How an Amortization Table Works

An amortization table lays out each scheduled payment and the loan balance after it. At the beginning of a standard amortizing loan, a larger portion of each payment goes toward interest because the balance is higher. As the balance falls, the interest portion generally decreases and more of the payment reduces principal.

For each month, the basic table calculations are:

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

For example, with a $20,000 starting balance and a monthly rate of 0.0066667, the first month’s interest is about $133.33. From a $405.53 payment, approximately $272.20 reduces principal, leaving a balance near $19,727.80. Later rows use the updated balance. A complete table repeats these steps for every payment; the calculator block above reports the payment and overall interest rather than displaying individual rows.

When to Use the Estimate and How to Read It

Use the calculation to understand how a proposed principal, APR, and term affect scheduled payments and interest under a simple fixed-rate model. It can also help you check a lender’s disclosed figures for broad consistency, provided you enter the same principal, rate, term, and payment frequency.

The monthly payment is not the same as the total cost of borrowing. Total interest estimates the interest across all scheduled payments, while the principal is the amount borrowed. The sum of principal and interest is the scheduled repayment total in this model. Charges outside the formula can increase the amount due or change the amount financed.

For a loan with fees or a different payment schedule, the result may not match the lender’s quoted payment. APR may reflect costs differently from a simple interest rate, depending on the loan’s terms and disclosures. Use the exact rate and fee information supplied for the specific loan, and compare figures on the same basis.

Common Calculation Problems and Limits

• Entering APR as a decimal: enter 8 for 8%, not 0.08. The formula divides the percentage by 1,200 to get a monthly decimal rate.
• Mixing years and months: the input is in years, and the formula converts it to monthly payments by multiplying by 12.
• Assuming the table predicts a payoff quote: a scheduled balance is not necessarily the amount needed to pay off a loan on a particular date. Accrued interest, fees, and payment timing can affect a payoff figure.
• Rounding each row: a manually built table may differ by a few cents if interest or balances are rounded at every step. Lenders’ calculation and rounding methods can also vary.

This formula is for a fixed rate and level monthly payments. It does not model variable rates, irregular payments, skipped payments, late charges, origination fees, or extra principal payments. For an interest-free loan, the formula’s division-by-rate form is not suitable; the basic payment would instead be principal divided by the number of payments. An actual disclosure or account statement is needed for loan-specific figures.

Frequently Asked Questions

Does this calculator show a full amortization table?
The calculator block computes the monthly payment and total interest. The explanation describes how to calculate each row, but the block itself does not output a month-by-month schedule.

Why does the interest portion decrease over time?
With a fixed rate, each period’s interest is calculated from the remaining balance. As principal is repaid, the balance falls, so the interest charged per period usually falls too.

Does APR include every loan cost?
Do not assume the calculator captures every charge. It accepts APR as an input but has no separate fee fields; consult the lender’s disclosure for the rate definition, fees, and payment details that apply to the loan.

Can I use the estimate for extra payments?
Not directly. The calculation assumes the same scheduled payment each month and does not account for extra principal, payment-date changes, or lender rules for applying additional amounts.

Why might my lender’s payment differ?
The lender may use a different amount financed, rate, term, payment date, fee treatment, or rounding method. Check that the inputs match the loan disclosure before comparing results.

The 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 | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2