Loan Calculator

Introduction

This Loan Calculator estimates the fixed monthly payment, total interest, and full repayment cost for a standard amortizing loan. Enter the principal, annual interest rate, and term in months to see how much each payment applies to interest versus principal over time. Use it when comparing personal loan offers, auto financing quotes, or any installment loan with equal monthly payments and no balloon balance.

Who this calculator is for

Borrowers who received a firm quote for a fixed-rate installment loan and want to verify the payment before signing belong here. That includes personal loans from banks and credit unions, unsecured lines converted to term loans, and some private student refinance products where the rate and term are fixed at origination.

It is also useful for co-borrowers splitting a household purchase when you need one number everyone can sanity-check against the lender disclosure. If you already know the payment and need to solve for term or rate instead, switch to the Payment Calculator. For revolving balances with minimum payments that change each month, use the Credit Card Calculator.

What it estimates

The engine uses the standard amortizing loan formula: payment equals principal times the monthly rate times one plus that rate raised to the number of payments, divided by one plus the rate raised to payments minus one. Each month, interest is charged on the remaining balance and the rest of the payment reduces principal. The schedule shows that split period by period.

Output includes monthly payment, total amount repaid, total interest, and an amortization table. Origination fees, prepayment penalties, insurance bundled into the note, and variable rates are not modeled. The calculator assumes payments arrive on time every month for the full term.

Inputs explained

Use the same units printed on your loan estimate or promissory note.

• Loan amount: The principal you borrow, not including fees you pay upfront out of pocket unless the lender finances them into the note.
• Annual interest rate: The nominal APR for a fixed-rate loan. For comparison across products, confirm whether the lender quoted APR or a lower note rate without fees.
• Loan term: Length in months. A four-year loan is 48 months, not 4 unless the form accepts years separately.
• Start date (optional): When the first payment is due, for schedule dating only; it does not change the math if rate and term are fixed.
• Extra payment (optional): A fixed amount added to each scheduled payment to see early payoff impact.

How to read the results

Monthly payment is the amount that clears the loan on schedule at the rate you entered. Total interest is the sum of every interest line in the schedule; on high-rate, long-term loans it can exceed principal. Early rows in the table show mostly interest; later rows shift toward principal. That pattern is normal for amortizing debt.

If two offers have similar payments but different terms, compare total interest, not just the monthly figure. A lower payment with a longer term often costs more over life. Cross-check the rate with the APR Calculator when fees are rolled into the loan.

Worked example

Enter a $18,000 personal loan at 11.5% APR for 48 months. Calculate. Monthly payment should land near $470. Total interest over four years approaches $2,560, meaning you repay about $20,560 in all. In month one, interest on $18,000 at 11.5% annual is roughly $172, so only about $298 of that first payment reduces principal.

Add $50 extra each month and recalculate. The loan should finish several months early and total interest drops by hundreds of dollars. Write both scenarios before you accept the lender's autopay offer.

Practical use cases

Compare a credit union personal loan with a promotional rate against a dealer's in-house financing on the same purchase price. Model whether consolidating two smaller debts into one new loan actually lowers total interest when the new term is longer.

Small business owners can rough-check an equipment installment quote before applying. Pair the result with your cash flow in the Budget Calculator to confirm the payment fits after housing and existing debt. Keep an emergency buffer; see how much to keep liquid.

Limitations and related tools

Balloon payments, interest-only periods, variable rates, and skipped-payment forbearance are not supported. Lenders may use slightly different rounding on the final payment or a 360-day year convention that moves totals by a few dollars.

For credit card revolving math, use the Credit Card Calculator. For paying multiple debts in a chosen order, try the Debt Payoff Calculator. For unsecured consumer quotes with origination fees, the Personal Loan Calculator adds fee-aware totals.

How It Works

1. Enter principal and APR. Type the loan amount and annual interest rate exactly as the lender quoted for a fixed-rate installment loan.
2. Set the term in months. Enter the number of monthly payments in the offer. Convert years to months if the form asks for months only.
3. Calculate and scan totals. Click Calculate. Read monthly payment, total interest, and total repaid before you open the amortization table.
4. Test an extra payment. Add a monthly extra amount you could sustain and calculate again. Compare months saved against your liquidity needs.

Formula and methodology

The Loan Calculator uses this identity for the scenario you enter. A bank, payroll system, or tax program may round on a 360-day year or average daily balance, so a statement can differ by a small amount.