How to Calculate a Loan Payment
Quick answer: To calculate a loan payment, you need three numbers: the loan amount, the annual interest rate, and the loan term in years. Put them into the standard amortization formula, or use the free Loan Calculator on SavyTools and let it do the maths for you. For example, a $20,000 loan at 6.5% over 5 years costs $391.32 a month, $23,479.38 in total, and $3,479.38 in interest. These figures are estimates for planning only, not financial advice. They cover principal and interest only, and do not include fees, taxes or insurance.
A loan payment looks simple. One number leaves your bank account every month, and the loan slowly shrinks. But that number hides three moving parts: how much you borrowed, what the lender charges you, and how long you take to pay it back.
This guide shows you the formula in plain words, a worked example, a 3-year versus 5-year comparison, what amortization means, and how to compare two offers fairly.
1. What you need before you calculate a loan payment
Every loan payment calculation starts with the same three inputs. If one is missing, you are guessing.
| Input | What it means | Where to find it |
|---|---|---|
| Loan amount | The amount you borrow, also called the principal | Your loan offer |
| Annual interest rate | The yearly cost of borrowing, as a percentage | Your loan offer |
| Loan term | How many years you take to repay the loan | Your loan offer |
Two habits make the answer more useful. First, always use the rate from your actual offer, not a guess or a rate from an advert. Second, remember the maths counts in months: a 5-year loan is 60 monthly payments, and a 3-year loan is 36.
Bullet summary
- You need three numbers: loan amount, annual interest rate, and loan term.
- Use the rate from your own offer, not a guessed rate.
- A 5-year loan means 60 monthly payments, a 3-year loan means 36.
2. The loan payment formula, in plain words
The standard formula for a fixed monthly loan payment is the amortization formula. Each part has a simple job.
M = P x [r(1+r)^n] / [(1+r)^n - 1]
| Symbol | Meaning |
|---|---|
| M | Monthly payment |
| P | Principal, the loan amount you borrow |
| r | Monthly interest rate, your annual rate divided by 12 |
| n | Number of monthly payments |
The monthly rate, r, turns your yearly rate into a monthly one. The number of payments, n, spreads the loan over the whole term. Together they give the one fixed monthly amount that pays off the full loan, with interest, by the last payment. The payment stays the same every month. Only the split between interest and principal changes, which section 6 explains.
You do not need to work this out by hand. The formula shows where the number comes from. For everyday use, the free Loan Calculator runs the same formula for you.
Bullet summary
- M is the monthly payment, P is the loan amount, r is the monthly rate, n is the number of payments.
- The monthly rate is the annual rate divided by 12.
- The formula finds one fixed payment that clears the loan by the final month.
3. Worked example: $20,000 at 6.5% for 5 years
Take a realistic example. You borrow $20,000 to buy a car at 6.5% annual interest, repaid over 5 years.
| Figure | Amount |
|---|---|
| Loan amount | $20,000 |
| Annual interest rate | 6.5% |
| Loan term | 5 years (60 monthly payments) |
| Monthly payment | $391.32 |
| Total paid over 5 years | $23,479.38 |
| Total interest | $3,479.38 |
That $3,479.38 is the real cost of borrowing here: the $20,000 you borrowed, plus $3,479.38 for the use of the lender’s money. The payment of $391.32 never changes during the 5 years, as long as the rate stays fixed.
Try the same numbers in the Loan Calculator to confirm the result.
Bullet summary
- $20,000 at 6.5% over 5 years costs $391.32 a month.
- Total paid is $23,479.38, so total interest is $3,479.38.
- The monthly payment stays fixed when the rate is fixed.
4. 3 years vs 5 years: what a shorter term really costs
The term is the lever most borrowers underestimate. A shorter term raises the monthly payment, but it cuts the total interest by a lot.
| Figure | 3 years (36 payments) | 5 years (60 payments) |
|---|---|---|
| Monthly payment | $612.98 | $391.32 |
| Total paid | $22,067.28 | $23,479.38 |
| Total interest | $2,067.28 | $3,479.38 |
The 3-year loan costs $221.66 more every month, but it saves $1,412.10 in total interest. That is the trade-off: pay more each month now, and pay much less overall.
Which term is right depends on your monthly budget, not on the maths alone. If $612.98 a month leaves you short for rent, food and other bills, the 5-year term is safer. Never pick a term by the monthly payment alone. Always look at the total interest next to it.
Bullet summary
- 3 years costs $612.98 a month and $2,067.28 in total interest.
- 5 years costs $391.32 a month and $3,479.38 in total interest.
- The shorter term saves $1,412.10 in interest but costs $221.66 more per month.
- Pick the term your monthly budget can carry, not just the lowest payment.
5. How to calculate a loan payment with the free Loan Calculator
If you want the answer without touching the formula, the SavyTools Loan Calculator does the whole job in your browser, with no sign-up and no account. It works for auto, personal and student loans.
- Choose the loan type: Auto, Personal or Student.
- Enter the loan amount in dollars.
- Enter the annual interest rate from your offer, for example 6.5.
- Enter the loan term in years.
- Press Calculate loan to see the monthly payment, total interest, total paid, and the full amortization schedule.
The schedule is the most useful part. It shows, for every payment, how much goes to principal and how much goes to interest.
Bullet summary
- Pick the loan type, then enter the amount, the rate and the term.
- The calculator shows the monthly payment, total interest and total paid.
- It also builds a full month-by-month amortization schedule.
6. What amortization means for your money
Amortization is the schedule that splits each monthly payment into interest and principal. Early on, most of your payment goes to interest, because the balance is at its largest. As the balance shrinks, the interest part shrinks, and more of each payment goes to principal.
Here are the first three payments on our $20,000 example. The monthly payment is $391.32 every time, but the split inside it moves a little each month.
| Payment | Interest part | Principal part | Balance left |
|---|---|---|---|
| Payment 1 | $108.33 | $282.99 | $19,717.01 |
| Payment 2 | $106.80 | $284.52 | $19,432.49 |
| Payment 3 | $105.26 | $286.06 | $19,146.43 |
The interest part falls from $108.33 to $105.26 in three months, while the principal part rises from $282.99 to $286.06. That slow shift is why a loan feels slow to shrink at the start.
Bullet summary
- Amortization splits each payment into interest and principal.
- Early payments are mostly interest, later payments are mostly principal.
- In payment 1 of our example, $108.33 is interest and $282.99 is principal.
7. How to compare two loan offers fairly
Two lenders can offer you the same $20,000 and quote very different monthly payments, because their rates or terms differ. Comparing offers by the monthly payment alone is the most common mistake borrowers make.
Compare offers on three numbers: the monthly payment, the total interest, and the total paid. The offer with the lowest total interest is the cheapest loan, even if its monthly payment is higher.
Here is a second worked check for any calculator. A $10,000 loan at 10% over 60 months costs $212.47 a month. If a tool gives you a very different number, its maths is wrong.
Keep the loan amount and the term the same while you compare, and change only the rate. Always use the rate from the written offer, not a rate from an advert.
Bullet summary
- Compare offers on monthly payment, total interest and total paid, not on the monthly payment alone.
- The lowest total interest is the cheapest loan.
- Keep the amount and the term the same while you compare, and change only the rate.
8. What your monthly payment does not include
The monthly payment from the formula covers principal and interest only, written as P and I. It does not include the other costs that often sit next to a loan, so do not treat it as your full monthly cost.
| Cost | Included in the monthly payment? |
|---|---|
| Principal | Yes |
| Interest | Yes |
| Lender fees | No |
| Taxes | No |
| Insurance | No |
For a car loan, insurance is usually a separate monthly cost, and some lenders charge fees on top of the loan. For a home loan, property taxes, homeowners insurance and HOA fees sit outside the principal and interest figure too. The SavyTools Mortgage Calculator works the same way, and taxes, insurance and HOA fees are not included. Budget for those costs separately.
Bullet summary
- The monthly payment covers principal and interest only.
- Fees, taxes and insurance are not included.
- Budget for those costs separately.
Frequently asked questions
What is the formula to calculate a loan payment?
The standard formula is M = P x [r(1+r)^n] / [(1+r)^n - 1]. M is the monthly payment, P is the loan amount, r is the monthly rate (annual rate divided by 12), and n is the number of payments. The free Loan Calculator runs the same formula for you.
Can I calculate a loan payment without a calculator?
Yes, but it is slow and easy to mistype. A calculator is faster and less error prone. Enter the amount, the annual rate and the term to get the monthly payment, the total interest and the full schedule.
Does the loan type change the monthly payment?
No. Auto, personal and student loans use the same calculation. On the SavyTools Loan Calculator the loan type is only a label.
Why is my first payment mostly interest?
Because the loan balance is at its largest in the first month. In our $20,000 example at 6.5%, the first $391.32 payment splits into $108.33 of interest and $282.99 of principal.
Is this financial advice?
No. This guide and the Loan Calculator give estimates for planning only, not financial advice and not a loan offer. A real lender’s quote will depend on your credit, the loan type and current rates.
Does the monthly payment include taxes and insurance?
No. The monthly payment covers principal and interest only, so budget for fees, taxes and insurance separately. The Mortgage Calculator follows the same rule.
Related guides
Planning a bigger purchase? The Mortgage Calculator estimates your monthly principal and interest payment for a US home loan, with taxes, insurance and HOA fees not included. To see how money grows instead of how a loan shrinks, try the Compound Interest Calculator. And if you are weighing a home purchase against your income, read How Much House Can I Afford?
