Loan and Debt Comparison Calculator

This loan and debt comparison calculator estimates the monthly payment and total interest for a fixed-rate loan from its amount, APR, and term. Enter those figures to see the scheduled payment and the interest charged over the full term; the results describe loan repayment, not every kind of debt.

Formula

The calculator uses the standard fixed-payment amortization formula. It first calculates a monthly payment, rounds that payment to cents, and then calculates total interest using the rounded payment.

• Monthly payment: M = round[P × r ÷ (1 − (1 + r)⁻ⁿ), 2]
• Total interest: I = M × n − P
• Monthly rate: r = APR ÷ 1,200
• Number of payments: n = term in years × 12

P is the original loan principal in dollars; APR is the annual percentage rate entered as a percentage; r is the monthly rate expressed as a decimal; n is the number of monthly payments; M is the monthly payment in dollars; and I is total interest in dollars. For the example APR of 8%, r is 0.08 ÷ 12, or approximately 0.0066667. The calculation assumes a regular monthly payment and a constant rate.

Worked Example

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

1. Substitute the values: M = 20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰].
2. The unrounded monthly payment is approximately $405.53; rounded to cents, it is $405.53 per month.
3. Total interest uses the rounded payment: $405.53 × 60 − $20,000 = $4,331.80.

The scheduled payments total $24,331.80, consisting of the $20,000 principal and $4,331.80 interest. Actual lender figures can differ because of payment dates, rounding conventions, fees, or contract terms.

Assumptions

• The interest rate remains fixed for the entire term.
• Payments are equal monthly installments, with the first payment one month after the loan begins.
• Interest is modelled monthly at APR divided by 12.
• Fees, taxes, insurance, PMI, escrow, late charges, and optional extra payments are not included.

Loan Versus Debt: What the Terms Mean

A loan is money borrowed under an agreement to repay it, usually with interest and a specified schedule. Debt is the broader obligation to repay money. A loan is therefore one kind of debt, while debt can also arise from a credit-card balance, an unpaid bill, or another borrowing arrangement. The precise terms and consequences depend on the agreement and applicable circumstances.

This distinction matters when comparing balances. A fixed-term personal loan may have regular payments and a planned payoff date. Credit-card debt may have a changing balance, a variable rate, and a minimum payment that does not retire the balance on a fixed schedule. The calculator models the first pattern; it does not model revolving balances or minimum-payment rules.

How to Compare Borrowing Costs

Monthly payment is useful for understanding the scheduled cash outflow, but it is not a complete measure of cost. A longer term usually spreads repayment across more months. That can reduce the calculated installment while increasing total interest, because interest accrues for longer. A shorter term generally produces larger installments but fewer periods of interest under the same fixed-rate assumptions.

For a meaningful comparison, use the same principal when comparing terms, and the same term when comparing rates. For each option, note the monthly payment and total interest together. Also check the lender’s written figures for fees and any charges that the formula omits. A quoted APR may not capture every cost in the same way across different products, so compare disclosures on a like-for-like basis rather than treating this estimate as a complete contract comparison.

• Payment: the modelled amount due each month, excluding omitted charges.
• Total interest: the modelled interest across all scheduled installments.
• Total scheduled payments: monthly payment multiplied by the number of payments; this includes principal and interest, not excluded fees.

Using the Calculator and Avoiding Misreadings

Enter the amount borrowed—not the amount you expect to pay in total—then enter the lender’s APR and the term in years. Convert a term stated in months to years by dividing by 12; for example, 36 months is three years. The calculator accepts terms from 0.0833 to 50 years and APR values from 0.01% to 100%. These are input limits for the calculation, not statements about products or approval criteria.

A frequent misconception is that the lower monthly payment necessarily means lower borrowing cost. It may simply reflect a longer repayment period. Another is to compare a loan’s payment with a credit-card minimum payment as if both schedules were equivalent. They are not: minimum payments and revolving balances require a different calculation, including assumptions about future spending and payment rules.

Rounding also matters. This calculator rounds the monthly installment to the nearest cent and uses that rounded amount to estimate total interest. A lender may calculate daily interest, use different rounding conventions, or adjust the final payment, so a small difference is possible. The estimate also assumes every payment is made on schedule and that the rate does not change.

Limits and Other Debt Comparisons

This tool is suited to a straightforward, fully amortizing fixed-rate loan with equal monthly payments. It is not a payoff planner for extra payments, a variable-rate forecast, a credit-card payoff calculator, or a comparison of all-in costs for secured borrowing. To compare debts with different structures, first identify each balance, rate, payment method, fees, and timing; then use a model designed for those features. Do not treat the results as a determination of eligibility or personal affordability.

For a loan offer, use the amount, APR, and term supplied in the lender’s disclosure, and review the complete payment schedule and any additional charges. If a rate or fee is not yet known, the calculator can only illustrate a hypothetical value; it cannot supply current market terms.

Frequently Asked Questions

Is a loan the same as debt?
No. A loan is a specific borrowing arrangement, while debt is the wider category of money owed. Loans are debt, but not every debt is structured as a term loan.

Does a lower monthly payment mean I pay less overall?
Not necessarily. A longer term can lower the scheduled monthly payment while increasing total interest. Compare both the installment and total cost, and account for charges excluded from this estimate.

Does this calculator include fees?
No. It calculates principal and interest from the entered APR and term. Fees, taxes, insurance, and other charges are not separate inputs and are not included in the displayed totals.

Can I use it for credit-card debt?
Not accurately for a revolving balance. Card balances can change with purchases, payments, and rate changes, and minimum-payment formulas differ. Use a calculator specifically designed for credit-card payoff estimates.

Why might my lender’s payment differ?
The agreement may use different rounding, payment dates, interest calculations, fees, or a non-fixed rate. Check the lender’s payment schedule for the contractual figures.

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

Related

• Online Installment Loan Rates: How APR Affects Payments
• Personal Installment Loan Payment Calculator
• Online Installment Loan Benefits and Payment Calculator

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