Free Loan Calculator — Monthly Payments, Interest & Amortization

Before you sign a loan agreement, you need to know exactly what it will cost. Not just the monthly payment — the total interest over the life of the loan, the amortization breakdown, and how different rates and terms change the math.

Our free loan calculator shows you all of this instantly. Plug in any loan amount, interest rate, and repayment term, and see your monthly payment, total interest paid, and a full amortization schedule. Works for mortgages, car loans, personal loans, student loans, and business loans.

How Loan Math Works

Most consumer loans use a fixed-rate amortization formula. The monthly payment is calculated as: M = P x [r(1+r)^n] / [(1+r)^n - 1], where P is the loan principal, r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments.

Take a $25,000 car loan at 6.5% APR for 5 years (60 months). The monthly rate is 0.065 / 12 = 0.00542. The monthly payment works out to $489.15. Over 60 months, you will pay $29,349 total — meaning $4,349 goes purely to interest. That is 17.4% of your original loan amount paid as the cost of borrowing.

Small changes in rate or term have outsized effects. That same $25,000 loan at 5.5% instead of 6.5% saves $714 in total interest. Stretching the term to 72 months drops the monthly payment by $70 but adds $1,400 in total interest. These tradeoffs are exactly what a loan calculator helps you visualize before committing.

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Amortization Explained

Amortization is the process of paying off a loan through equal installments over time. Each payment covers two things: interest owed on the remaining balance and a portion of the principal. The split between these two changes with every payment.

In the early months, most of your payment goes toward interest because the outstanding balance is large. As the balance shrinks, less interest accrues each month, so a larger share of each payment goes toward reducing the principal. By the final payments, almost everything goes to principal.

This is why extra payments early in a loan save far more money than extra payments later. A $200 extra payment in month 3 of a 30-year mortgage reduces the total interest by thousands of dollars because that $200 no longer accrues compound interest for the remaining 29+ years.

Fixed vs. Variable Interest Rates

A fixed-rate loan locks your interest rate for the entire term. Your monthly payment stays the same from the first month to the last. This makes budgeting simple and protects you from rate increases. Most mortgages, auto loans, and personal loans offer fixed rates.

A variable-rate loan (also called adjustable-rate) has an interest rate that changes periodically based on a benchmark rate like the prime rate or SOFR. Variable-rate loans often start with a lower introductory rate, but that rate can increase — sometimes significantly — when the adjustment period hits.

The general rule: choose fixed rates when rates are low and you want predictability. Consider variable rates only if you plan to pay off the loan quickly (before adjustments kick in) or if current fixed rates are unusually high and you expect them to drop.

Tips to Lower Your Monthly Payments

• Extend the term: A longer repayment period lowers monthly payments but increases total interest. A 30-year mortgage has lower payments than a 15-year, but you pay roughly double the total interest.
• Improve your credit score: Even a 50-point improvement can qualify you for a noticeably lower rate. Pay down credit card balances and avoid new credit inquiries before applying.
• Make a larger down payment: Borrowing less means paying less. On a mortgage, 20% down also eliminates private mortgage insurance (PMI), saving you $50 to $200 per month.
• Refinance when rates drop: If market rates fall 0.75% or more below your current rate, refinancing often pays for itself within 12 to 18 months. Use a calculator to verify the break-even point.
• Biweekly payments: Paying half your monthly payment every two weeks results in 26 half-payments per year — equivalent to 13 full payments instead of 12. This one trick shaves years off a 30-year mortgage.

Frequently Asked Questions

How are monthly loan payments calculated?

Monthly payments on a fixed-rate loan are calculated using the amortization formula: M = P x [r(1+r)^n] / [(1+r)^n - 1], where P is the principal, r is the monthly interest rate (annual rate divided by 12), and n is the total number of payments. Our calculator does this math instantly for any loan amount, rate, and term.

What is amortization?

Amortization is the process of spreading loan repayment over time through equal monthly installments. Each payment covers both interest and principal, but the split changes over the life of the loan. Early payments are mostly interest; later payments are mostly principal. An amortization schedule shows this breakdown for every single payment.

How can I reduce total interest paid on a loan?

Four proven strategies: choose a shorter loan term (a 15-year mortgage saves tens of thousands compared to a 30-year), make extra payments toward principal (even small amounts compound over time), refinance to a lower interest rate when rates drop, and make biweekly payments instead of monthly (this adds one extra full payment per year).

What is the difference between fixed and variable rate loans?

A fixed-rate loan locks in the same interest rate for the entire term — your monthly payment never changes. A variable-rate (adjustable-rate) loan has an interest rate that changes periodically based on market conditions. Variable rates often start lower but can increase significantly. Fixed rates provide predictability; variable rates carry risk but may cost less if rates stay low.