Loan Payment Calculator

What this calculator does

The Loan Payment Calculator answers one of the most common money questions there is: if I borrow this much, at this rate, for this many years, what is the monthly payment, and how much will I pay in total? You enter three numbers, and it gives you back three: the fixed monthly payment, the total amount you'll repay over the life of the loan, and the total interest baked into that figure.

It models a standard fully-amortizing fixed-rate loan with monthly payments. It is the same kind of math your bank uses for a mortgage, an auto loan, a personal loan, or a student loan in repayment. There is no calculate button. Type the three numbers, and the results appear underneath.

Who actually uses this

The honest list is short and practical:

• House shoppers sanity-checking whether a price they keep seeing on Zillow turns into a payment they can stomach.
• People comparing two loan offers with different rates or terms, trying to see which one costs less per month and which costs less overall.
• Anyone considering a 15-year vs 30-year mortgage, or a 48-month vs 72-month car loan, who wants to feel the trade-off in actual dollars before talking to a lender.
• Borrowers thinking about paying extra each month and wondering what shaving a few years off the term would do.
• Students and parents running numbers on a private student loan or a consolidation loan.

If your monthly bill includes property taxes, insurance, or PMI — which is true for almost every real mortgage — this isn't the right tool by itself. Use the Mortgage Calculator for that. This one is principal and interest only, which is also exactly what you want when you're comparing two raw loan offers side by side without the noise.

How to use it

Three fields, all required:

• Loan Amount: the principal you're actually borrowing, in dollars. For a mortgage, that's the home price minus your down payment, not the home price itself. Type it as a plain number: 250000, not $250,000 or 250k.
• Annual Interest Rate: the nominal yearly rate, as a percent. Type 6.5 for 6.5%, not 0.065. This should be the loan's stated interest rate from your rate sheet or loan estimate, not the APR (more on that distinction below).
• Loan Term: how long you have to pay it back, in years. 30 for a 30-year mortgage, 5 for a 5-year auto loan, 10 for a typical student-loan repayment plan. For loans you usually think of in months, divide by 12. A 72-month car loan is 6 years.

The results panel appears as soon as all three fields hold a non-zero number. If any one of them is blank, zero, or non-numeric, the panel stays hidden — that's a deliberate guardrail, not a bug.

How it works

Under the hood the calculator uses the standard fixed-rate amortization formula:

M = P · [ r(1 + r)n ] / [ (1 + r)n − 1 ]

where:

• P is the principal — what you typed in Loan Amount.
• r is the monthly interest rate, which the calculator gets by dividing your annual rate first by 100 (to turn 6.5 into 0.065) and then by 12 (to turn it into a monthly rate). At 6.5% annual, r is roughly 0.005417.
• n is the total number of monthly payments, i.e. your term in years multiplied by 12. A 30-year loan has n = 360; a 5-year loan has n = 60.

From the monthly payment M, the other two figures fall out by simple arithmetic:

• Total Amount Paid = M × n, the payment times the number of months. This is every dollar you'll send the lender over the life of the loan.
• Total Interest Paid = (M × n) − P, what you paid them minus what you originally borrowed. That difference is the lender's cut.

The model assumes a level payment that never changes, monthly compounding, and that you pay on time every single month for the full term. Early payments are mostly interest because the balance is high; later payments are mostly principal because the balance has shrunk. Add them all up and the loan is exactly paid off on the last month.

A worked example

Take the placeholder values: $250,000 at 6.5% for 30 years.

• P = 250,000
• r = 6.5 ÷ 100 ÷ 12 ≈ 0.005417
• n = 30 × 12 = 360
• (1 + r)360 ≈ 6.992

Plug into the formula and you get a monthly payment of $1,580.17. Multiply by 360 months for a total paid of $568,861.22. Subtract the original $250,000 and the total interest is $318,861.22 — meaning you'll pay back roughly $1.27 in interest for every $1 you borrowed, spread over thirty years.

That last number is the one that tends to shock people. It's also the single best argument for shopping the rate, putting more down, or shortening the term if you can.

The 15-vs-30 trade-off, in real numbers

The same $250,000 loan at the same 6.5% rate, but over 15 years instead of 30, comes out to a monthly payment of roughly $2,178. That's about $598 more per month — uncomfortable for a lot of households. But the total interest paid drops to roughly $142,000, against $318,861 on the 30-year. Same loan, same rate, just a shorter term — and you save roughly $177,000 in interest.

Run the numbers yourself with your own loan amount and rate. The point isn't that one term is right and the other is wrong. It's that the comparison is concrete and easy to see in this tool, and most people never actually do it.

Common pitfalls

• Entering the rate as a decimal. Type 6.5, not 0.065. If your monthly payment comes back looking absurdly low (like ten dollars on a quarter-million-dollar loan), this is almost certainly why.
• Confusing APR with the interest rate. The APR you see on a loan estimate includes certain lender fees rolled in, so it runs a bit higher than the loan's actual interest rate. APR is useful for comparing offers; it's the wrong number for computing a payment. Use the interest rate.
• Entering term in months instead of years. The field is years. A 60-month car loan is 5, not 60. Entering 60 will model a sixty-year loan and give you a payment that doesn't make sense.
• Forgetting that this is principal and interest only. A mortgage payment in the real world also includes property tax, homeowner's insurance, often PMI, and sometimes HOA dues. Auto loans usually don't bundle anything else in, but they may add gap insurance or extended warranties to the financed amount. If your "real" payment looks higher than what this tool returns, that's why, and that's normal.
• Trying to model a 0% loan. The formula divides by the rate, so it can't run at exactly 0%, and the calculator hides the result whenever any field is zero. For a true 0% promotional loan, the math is just principal divided by months: $12,000 over 24 months is $500 a month.

When NOT to use it

This calculator is built for one specific kind of loan: fixed-rate, fully amortizing, equal monthly payments. It's the right tool for most consumer loans. It's the wrong tool for:

• Adjustable-rate mortgages (ARMs). The rate changes after an introductory period, so a single fixed rate doesn't describe the whole loan.
• Interest-only loans. You pay only interest for a stretch, then either pay the principal in a balloon or refinance. The amortization math doesn't apply during the interest-only phase.
• Income-driven student loan repayment plans (IBR, PAYE, SAVE, etc.). Those cap the payment at a percentage of your income rather than amortizing the balance, and they have forgiveness mechanics this tool doesn't model.
• Credit cards and other revolving debt. There's no fixed term — the "payoff time" depends on how much you choose to pay each month and what new charges you add.
• Loans with balloon payments or any non-standard payoff structure.

For any of those, you want a more specialized calculator — or, honestly, a conversation with the lender about what your actual schedule will look like.

What if the answer looks wrong?

Quick gut checks:

• Payment seems way too low. You probably entered the rate as a decimal (0.065 instead of 6.5), or the term in months instead of years.
• Payment seems way too high. You may have added an extra zero to the loan amount, or you have the term too short. A 5-year mortgage payment is very different from a 30-year one.
• Total interest is more than the principal. This is normal on a long mortgage at a non-trivial rate. At 6.5% over 30 years, you really do pay roughly $1.27 in interest per $1 borrowed.
• Result doesn't match your lender's quote exactly. Expect to be within a few dollars, not exact to the penny. Lenders round, they may treat the final payment differently to clear any leftover balance, and some loans use slightly different day-count conventions. Use this for sanity-checking and comparison, not as the legal payment amount.

Adjacent concepts worth knowing

• Amortization schedule. The month-by-month breakdown of how each payment splits between interest and principal, and what your remaining balance is after each one. This calculator gives you the headline numbers; an amortization schedule shows the inside.
• APR vs. interest rate. Both are quoted in percent, both look similar at a glance. APR is meant for comparing total cost of borrowing including certain fees; interest rate is what drives the payment math. Lenders are required to disclose APR specifically so you can compare offers on equal footing.
• Total interest as a percent of principal. Useful framing: at a given rate, the longer the term, the more interest you'll pay as a share of what you borrowed. Comparing this ratio across two offers is sometimes more illuminating than comparing monthly payments.
• Prepayment. On most amortizing loans, paying extra principal early saves a disproportionate amount of interest, because it cuts the balance that future interest is computed against. The tool here doesn't model extra payments directly, but you can re-run it with a shorter term to approximate the effect of paying down faster.

Related tools

If you're working through housing numbers, the Mortgage Calculator adds property tax, homeowner's insurance, and PMI on top of the principal-and-interest math you see here. For an auto loan specifically, the Car Loan Calculator uses the same amortization formula but with defaults sized for a typical car purchase.