How to Calculate Loan Payments: Complete Guide
A loan payment is the fixed monthly amount you pay to a lender to repay borrowed money plus interest over a set period. Most loans (mortgages, auto, personal) use the amortization formula to calculate equal monthly payments that gradually shift from mostly interest to mostly principal over the life of the loan.
Quick Answer
- 1. Formula: M = P[r(1+r)n] / [(1+r)n - 1], where P = principal, r = monthly rate, n = total payments.
- 2. Average 2026 rates: 6.22% (30-yr mortgage), 6.37% (new auto), 12.26% (personal loan), per Freddie Mac and Bankrate.
- 3. A 30-year $300K mortgage at 6.5% costs $382,633 in interest alone, more than the original loan.
- 4. Cutting the term from 30 to 15 years saves over $200,000 in total interest on a typical mortgage.
Calculate your loan payment in seconds
Enter the loan amount, rate, and term to see your monthly payment, total interest, and full amortization schedule.
The Loan Payment Formula Explained
The standard formula for calculating a fixed monthly loan payment is:
M = P[r(1+r)n] / [(1+r)n - 1]
Where:
- M = monthly payment
- P = principal (the total amount borrowed)
- r = monthly interest rate (annual rate / 12)
- n = total number of payments (loan term in years x 12)
Step-by-Step Calculation Example
Let us calculate the monthly payment on a $250,000 mortgage at 6.5% interest for 30 years.
Step 1: Convert the Annual Rate to Monthly
r = 6.5% / 12 = 0.065 / 12 = 0.005417
Step 2: Calculate Total Number of Payments
n = 30 years x 12 months = 360 payments
Step 3: Plug Into the Formula
M = 250,000 x [0.005417 x (1.005417)360] / [(1.005417)360 - 1]
(1.005417)360 = 6.9916
M = 250,000 x [0.005417 x 6.9916] / [6.9916 - 1] = 250,000 x [0.03788] / [5.9916] = 250,000 x 0.006321 = $1,580.17
Step 4: Calculate Total Interest
Total paid = $1,580.17 x 360 = $568,861. Total interest = $568,861 - $250,000 = $318,861.
How Different Loan Types Compare
Interest rates vary significantly by loan type. Here are average rates as of early 2026:
| Loan Type | Avg. Rate (2026) | Typical Term | Example Payment |
|---|---|---|---|
| 30-year mortgage | 6.22% | 30 years | $1,836/mo on $300K |
| 15-year mortgage | 5.54% | 15 years | $2,451/mo on $300K |
| New auto loan | 6.37% | 5-6 years | $488/mo on $30K (60 mo) |
| Used auto loan | 11.26% | 4-5 years | $552/mo on $20K (48 mo) |
| Personal loan | 12.26% | 3-5 years | $334/mo on $10K (36 mo) |
| Student loan (federal) | 6.53% | 10 years | $340/mo on $30K |
Source: Freddie Mac (mortgage), Bankrate (auto, personal), Federal Student Aid (student loans) as of March 2026.
How Interest Rate Affects Your Payment
Even small rate differences compound dramatically over long loan terms. Consider a $300,000 30-year mortgage:
| Interest Rate | Monthly Payment | Total Interest Paid |
|---|---|---|
| 5.0% | $1,610 | $279,767 |
| 5.5% | $1,703 | $313,212 |
| 6.0% | $1,799 | $347,515 |
| 6.5% | $1,896 | $382,633 |
| 7.0% | $1,996 | $418,527 |
The difference between 5% and 7% on a $300,000 loan is $386 per month and $138,760 in total interest over 30 years. This is why shopping for even a quarter-point lower rate is worth the effort.
How Loan Term Affects Total Cost
Shorter terms mean higher monthly payments but dramatically less interest:
| Term | Monthly Payment | Total Interest | Total Cost |
|---|---|---|---|
| 15 years (6.0%) | $2,532 | $155,683 | $455,683 |
| 20 years (6.0%) | $2,149 | $215,838 | $515,838 |
| 30 years (6.0%) | $1,799 | $347,515 | $647,515 |
Choosing a 15-year term over a 30-year term on $300,000 at 6% saves $191,832 in interest, despite the monthly payment being $733 higher.
Understanding Amortization
Amortization is the process by which each monthly payment splits between interest and principal. In the early years of a loan, most of your payment goes toward interest. As the principal balance decreases, the interest portion shrinks and the principal portion grows.
On a $300,000 mortgage at 6.5% for 30 years, your first monthly payment of $1,896 breaks down as: $1,625 interest and only $271 principal. By month 180 (halfway through), the split is roughly $1,096 interest and $800 principal. In the final year, nearly the entire payment goes to principal. This front-loading of interest is why extra principal payments early in the loan save the most money.
Strategies to Pay Off Loans Faster
- Biweekly payments: Pay half the monthly amount every two weeks. This results in 26 half-payments (13 full payments) per year instead of 12, effectively making one extra payment annually. On a 30-year mortgage, this can shave 4 to 5 years off the loan.
- Round up payments: If your payment is $1,580, round up to $1,600 or $1,700. The extra goes directly to principal.
- Apply windfalls to principal: Tax refunds, bonuses, and gifts directed at principal reduce the balance and save interest for the remainder of the loan.
- Refinance when rates drop: If rates fall at least 0.75% to 1% below your current rate, refinancing can reduce your payment and total interest (factor in closing costs, typically 2-5% of the loan).
The Bottom Line
The loan payment formula is the same whether you are buying a home, a car, or consolidating debt. The three levers you control are the amount borrowed, the interest rate (influenced by your credit score and market conditions), and the loan term. Shorter terms and lower rates save the most money. Use our free loan calculator to run the numbers, or view a full payment schedule with our amortization calculator.
Frequently Asked Questions
What is the formula for calculating monthly loan payments?
The standard amortization formula is M = P[r(1+r)^n] / [(1+r)^n - 1], where M is the monthly payment, P is the loan principal (amount borrowed), r is the monthly interest rate (annual rate divided by 12), and n is the total number of payments (loan term in months). For a $25,000 car loan at 7% APR for 60 months, r = 0.07/12 = 0.005833 and n = 60, giving M = $495.03 per month.
How does the loan term affect my monthly payment?
Longer loan terms mean lower monthly payments but significantly more total interest. For example, a $300,000 mortgage at 6.5%: a 30-year term gives a $1,896 monthly payment with $382,633 in total interest, while a 15-year term costs $2,613 per month but only $170,355 in total interest. That is a savings of $212,278 by choosing the shorter term, despite the higher monthly payment. Choose the shortest term you can comfortably afford to minimize total cost.
What is the difference between interest rate and APR?
The interest rate is the cost of borrowing the principal amount, expressed as a percentage. The Annual Percentage Rate (APR) includes the interest rate plus other fees and charges (like origination fees, closing costs, and mortgage insurance) spread over the life of the loan. APR gives a more complete picture of the total borrowing cost. For mortgages, the difference between rate and APR is typically 0.1% to 0.5%. Always compare APRs when shopping for loans because two loans with the same interest rate can have different APRs due to varying fees.
Can I lower my monthly loan payment after taking out the loan?
Yes, through several strategies. Refinancing replaces your current loan with a new one at a lower rate or longer term, which can reduce monthly payments (though extending the term increases total interest). Some lenders offer loan modification programs that adjust the terms of your existing loan. Making extra payments toward principal does not lower your required monthly payment but reduces the total number of payments and interest paid. For federal student loans, income-driven repayment plans can cap payments at 10-20% of discretionary income.
What credit score do I need for the best loan rates?
For the best rates on most loan types, you generally need a FICO score of 740 or higher. Mortgage lenders typically offer their best rates to borrowers with scores above 760. Auto lenders offer prime rates starting at around 720. Personal loan lenders vary, but top-tier rates usually require 720 or above. According to Bankrate, the average new car loan rate for borrowers with excellent credit (750+) was about 5.1% in early 2026, compared to 11.5% for borrowers with poor credit (below 600), a difference of over 6 percentage points that can cost thousands over the life of the loan.
Calculate your monthly loan payment
Enter the loan amount, interest rate, and term to see your payment, total interest, and amortization schedule.
Loan Calculator - Free