Loan Calculator - Payments, Payoff & Amortization
Calculate a fixed loan payment, model extra-payment payoff, estimate an affordable loan amount, compare offers, and inspect annual or monthly amortization.
Loan payment and early payoff planner
Estimate a fixed monthly payment, then test recurring and one-time principal payments without changing the required payment.
Loan amount from a monthly budget
Reverse the amortization formula to estimate the principal supported by a target payment, rate, term, and fee treatment.
Compare two fixed-rate loan offers
Compare monthly payment and projected cash cost using the same requested amount. Fees are added to each offer's financed balance.
Offer A
Offer B
Balance with and without extra payments
Calculation breakdown
Annual amortization summary
| Year | Payments | Principal | Interest | Ending balance |
|---|
Loan payment formula
A fixed-rate installment payment is calculated from the financed balance, monthly interest rate, and number of payments. At 0% interest, the balance is divided evenly across the selected term.
Amortization schedule
Each payment first covers the month's interest; the remainder reduces principal. Early payments usually contain more interest because the outstanding balance is higher. The annual and monthly tables show that shift over time.
Extra payments and early payoff
Recurring and one-time extras are applied to principal after the scheduled payment. The planner keeps the required payment unchanged and estimates the shorter payoff period and interest saved for a simple-interest amortizing loan.
Origination fees and APR
A financed fee increases the balance used for payment calculations; an upfront fee increases cash paid at closing. A lender's disclosed APR may already reflect fees, so set the separate fee to zero if adding it would count the same cost twice.
Find a loan amount
Budget mode reverses the payment formula. It estimates the maximum requested principal that fits the entered monthly payment, term, rate, and fee treatment. Approval and lender underwriting are not modeled.
Compare loan offers
A lower rate does not always mean a lower monthly payment because term and fees matter. Compare projected total payments and monthly cash flow, then verify prepayment rules and official disclosures with each lender.
Loan calculator formulas
| Metric | Formula |
|---|---|
| Monthly payment | P x r / (1 - (1 + r)^-n) |
| 0% payment | Financed balance / months |
| Monthly interest | Opening balance x annual rate / 12 |
| Principal paid | Payment - monthly interest + extra principal |
| Affordable balance | Payment x (1 - (1 + r)^-n) / r |
| Interest saved | Scheduled interest - accelerated interest |
Frequently asked questions
Does an extra payment lower the required monthly payment?
Not in this planner. Extra principal shortens payoff while the original required payment remains unchanged. Some lenders may recast a loan under separate rules.
Why is the first payment mostly interest?
Interest is calculated from the outstanding balance. The balance is largest at the beginning, so more of early payments goes to interest.
Should I enter the interest rate or APR?
Use the rate applied to the outstanding balance. If the quoted APR already includes an origination fee, avoid adding that fee again unless you intentionally want a conservative estimate.
Does this include late fees or prepayment penalties?
No. The model assumes on-time monthly payments, a fixed rate, and no penalty. Check the lender's contract before relying on an accelerated payoff estimate.
Method and sources
The Consumer Financial Protection Bureau amortization guide explains how fixed payments shift from interest toward principal. Its loan key terms explains APR, fees, and amount financed. Results are planning estimates, not lending, legal, tax, or financial advice.
Related calculators
Use the car loan calculator for trade-in and vehicle taxes, the mortgage calculator for housing and escrow costs, or the compound interest calculator for savings growth.
