Loan Payment Calculator

How to use the loan payment calculator

Enter the loan amount, the annual interest rate as a percent, and the term in years, then read off your monthly payment. The defaults stand in for a common case: a $25,000.00 loan at 6.5% over 5 years comes to $489.15 a month. Drag the term slider or retype any field and the payment updates immediately, so you can feel how each input pushes the number up or down before you ever sign anything.

This is a generic installment-loan calculator — the kind of math behind an auto loan, a personal loan, or a student loan. It assumes a fixed rate and equal monthly payments for the life of the loan, which is exactly how those loans are usually written. It is deliberately not a mortgage calculator: it leaves out property taxes, homeowners insurance, PMI, and escrow, all of which a dedicated mortgage tool handles. If you are pricing a home loan, reach for that one instead.

Below the payment you will also see the total amount paid and the total interest over the full term. Those two numbers are where the real cost lives. On the default loan you pay about $29,349.00 in total, which means roughly $4,349.00 of interest on top of the $25,000.00 you borrowed. The monthly figure alone can look affordable while the total interest quietly tells a different story, so it is worth glancing at both.

There are really only two levers, and it helps to test them one at a time. A lower rate or a shorter term both cut the total interest you pay. The trade-off is the monthly payment: a shorter term raises it because you are clearing the same balance faster, while stretching the term lowers the monthly payment but costs far more interest overall, because the balance sits there earning interest for longer. Try nudging the rate down a point, then try trimming a year off the term, and watch which one your budget can actually absorb.

To run your own loan, drop in the amount you plan to borrow, the rate your lender quoted, and the number of years, and let the slider sweep from a 1-year payoff to a long 30-year stretch. The result is an estimate for general information — your actual loan may add origination fees, a different compounding convention, or other charges — but it is an honest, apples-to-apples way to compare offers and decide what you can comfortably carry each month.

The formula

A fixed-rate loan uses the standard amortization formula: one level payment that fully retires the balance over n months. Convert the annual rate to a monthly rate and the term to months, then solve for the payment:

i = annual rate ÷ 12 ÷ 100      n = years × 12
payment = P × i × (1 + i)^n ÷ ((1 + i)^n − 1)      (if i = 0 → P ÷ n)
total paid = payment × n
total interest = total paid − P

Worked example with the defaults — $25,000.00 at 6.5% over 5 years: the monthly rate is i = 6.5 ÷ 12 ÷ 100 = 0.0054167 and the term is n = 5 × 12 = 60 payments. Running those through the formula gives a payment of $489.15 a month. Over all 60 payments that is about $29,349.00 paid in total, of which roughly $4,349.00 is interest on top of the $25,000.00 you borrowed.

Although the payment never changes, what each one buys does. Early on the balance is large, so most of the payment goes to interest and only a little to principal — amortization front-loads the interest. As the balance shrinks, the interest portion falls and more of each level payment chips at the principal, until the final payments are almost all principal. That is why paying a loan off early saves the most when you do it early: you skip the months when interest is taking the biggest bite.

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