Loan Calculator
Loan Details
Results
| Monthly Payment | — |
|---|---|
| Total Interest | — |
| Total Payment | — |
How to Use This Loan Calculator
Lenders quote a rate and term, but the number that actually matters is what leaves your account every month—and how much of that is interest you will never get back. I use this as the baseline before comparing offers: punch in amount, rate, and years, then sanity-check the payment against your budget.
- Enter loan amount. The principal you plan to borrow before fees.
- Enter interest rate. Annual percentage as quoted by the lender (e.g. 7.5%).
- Enter loan term in years. Typical personal loans run 3–5 years; auto loans often 5–7.
- Toggle amortization preview. Check the box to see the first 12 months of principal vs interest split.
- Press Calculate. Review monthly payment, total interest, and total payment over the full term.
Already carrying a balance and know months remaining? Use the Repayment Calculator. Need to work backwards from a payment budget? Try the Payment Calculator.
Loan Formulas and Practical Applications
A fixed-rate installment loan spreads repayment into equal monthly payments. Early payments are mostly interest; later ones chip away at principal faster—a pattern visible in the amortization preview.
Monthly payment
M = P × [ i(1 + i)ⁿ ] / [ (1 + i)ⁿ − 1 ]
Where P is loan amount, i is monthly rate (annual ÷ 100 ÷ 12), and n is term in months. On $25,000 at 7.5% over 5 years, payment is about $501/month.
Total interest
Total Interest = (M × n) − P
That same $25,000 loan costs roughly $5,060 in interest over five years—money that does not reduce what you owe.
Comparing term lengths
Stretching the term lowers the monthly payment but raises total interest. Run the same amount at different year counts side by side before signing—the payment difference can be smaller than the interest gap.
Frequently Asked Questions
How is the monthly loan payment calculated?
The payment uses standard fixed-rate amortization: loan amount, annual interest rate converted to a monthly rate, and term in years multiplied by 12 for months.
What does total interest include?
Total interest is the sum of all interest portions across every monthly payment over the full term, assuming on-time fixed payments with no prepayments.
What is the amortization preview?
When enabled, the calculator shows the first 12 months of payment split between principal and interest plus the remaining balance after each month.
Does this calculator include origination fees?
No. Enter the net amount financed. Lender origination fees, insurance, and taxes are not added automatically.
Can I use this for any fixed-rate installment loan?
Yes. Any loan with equal monthly payments and a fixed annual rate can be modeled here, from personal loans to equipment financing.