Calculators guide
Shorter or Longer Loan Term? How to Compare the Real Cost
· 4 min read
A longer loan term lowers your monthly payment but raises the total interest you pay, often dramatically. On a 300,000 loan at 6%, a 30-year term costs about 1,799 a month and 347,515 in interest; a 15-year term costs about 2,532 a month and 155,683 in interest. The right choice depends on whether the higher payment fits your budget comfortably, and what else you could do with the difference.
The figures below are calculations for comparison only, not financial advice. Real loan offers include fees, insurance and terms a calculator cannot see.
How is a monthly loan payment calculated?
Fixed-rate loans use the standard amortization formula:
Payment = P × r ÷ (1 − (1 + r)^−n)
- P is the amount borrowed.
- r is the monthly interest rate: the annual rate ÷ 12. At 6% a year, r = 0.005.
- n is the number of monthly payments: years × 12.
Each payment is the same size, but what it pays for changes. Interest is charged on the remaining balance, so early payments are mostly interest and later ones are mostly principal.
The 15-year vs 30-year comparison
Same loan, 300,000 at 6% a year, two terms:
| 30 years | 15 years | |
|---|---|---|
| Monthly payment | 1,798.65 | 2,531.57 |
| Number of payments | 360 | 180 |
| Total interest | 347,514.57 | 155,682.69 |
| Total amount paid | 647,514.57 | 455,682.69 |
The shorter term costs 732.92 more each month but saves 191,831.88 in interest. On the 30-year loan, total interest is larger than the original loan.
The first-year amortization tells the same story. On the 30-year loan, year one pays 17,899.78 in interest and only 3,684.04 off the balance. On the 15-year loan, year one pays 17,653.84 in interest and 12,725.00 off the balance, more than three times as much principal.
How to decide between terms
Ask these questions in order:
- Can you afford the shorter-term payment with room to spare? Base this on a realistic budget, including an emergency fund. A payment you can only just make is a risk if income drops.
- Does the lender charge for overpayments? If not, a longer term with voluntary extra payments gives you flexibility: you can pay like a short loan in good months and fall back to the lower required payment when you need to.
- Is the rate different for each term? Shorter terms often come with lower rates, which widens the gap further. Run both rates through the calculator.
- What would you do with the difference? If the monthly saving from a longer term would genuinely be invested, the comparison becomes closer. If it would simply be spent, the shorter term usually wins.
How to use the Loan Calculator
The Loan Calculator has three inputs:
- Enter the Loan amount, the Annual interest rate in percent, and the Loan term in years. Fractional terms such as 2.5 years are rounded to the nearest whole month.
- Read the Monthly payment, Total interest, Total amount paid and Number of payments.
- Open the Yearly amortization table to see principal paid, interest paid and remaining balance at the end of each year.
To compare terms, change only the term and note the results side by side. The default example, 250,000 at 4.5% over 25 years, comes out at 1,389.58 a month.
A 0% rate works too: a 20,000 loan over 4 years at 0% is simply 20,000 ÷ 48 = 416.67 a month.
What the calculator leaves out
It calculates principal and interest only. Your real monthly cost may also include:
- Property taxes and homeowners insurance (often collected with a mortgage payment)
- Mortgage insurance on low-down-payment loans
- Origination fees, closing costs, or account fees
- Rate changes on adjustable-rate loans
Add those separately when you budget. For loans quoted in months, such as car and personal loans, the EMI Calculator gives a month-by-month schedule. To see the other side of the coin, money growing at interest instead of costing it, try the Compound Interest Calculator.
FAQ
Why does my lender's quote differ slightly from the calculator?
Lenders may round each month's interest, use a different day-count convention, or include fees in the payment. Differences of a few cents to a few units are normal; large differences usually mean fees or insurance are included.
Does paying extra each month really help?
Yes. Every extra amount goes straight to the principal, so it reduces all future interest charges on that money. Check that your loan has no prepayment penalty first.
Is APR the same as the interest rate?
No. The interest rate is what you enter here. APR also folds in certain fees, so it is usually a little higher and is better for comparing offers between lenders.
Compare loan terms side by side with the Loan Calculator.