How to Use This Loan Calculator
This loan calculator finds your monthly payment, total interest, and total cost for any personal loan, auto loan, or installment loan. Enter your loan amount, annual interest rate, and loan term in months to instantly see your monthly payment, total interest, and total cost. The calculator also accepts an optional extra monthly payment — enter any amount above zero to see how much time and interest you save. Results update in real time, and the full year-by-year amortization schedule appears below the result cards.
The loan term field accepts any number of months. Common terms: 12 months (1 year), 24 months (2 years), 36 months (3 years), 48 months (4 years), 60 months (5 years), and 84 months (7 years). A hint below the field shows the equivalent in years and months as you type.
How Loan Payments Are Calculated
This calculator uses the standard installment loan amortization formula: M = P × r(1+r)^n / ((1+r)^n − 1), where M is the monthly payment, P is the principal (loan amount), r is the monthly interest rate (annual rate ÷ 12), and n is the number of monthly payments. The result is a fixed monthly payment that does not change over the life of the loan.
Like a mortgage, early loan payments are weighted heavily toward interest. On a $25,000 loan at 8.5% for 60 months, approximately $177 of the first payment goes to interest and $336 to principal. By the final payment, nearly the entire amount goes to principal. This front-loaded interest structure is why paying extra early has a disproportionate impact on total interest paid.
The True Cost of Loan Term Length
Stretching a loan over a longer term lowers the monthly payment but significantly increases total interest paid. Consider a $20,000 auto loan at 9% APR:
- 36 months: ~$636/month — $2,906 total interest
- 48 months: ~$498/month — $3,897 total interest
- 60 months: ~$415/month — $4,900 total interest
- 72 months: ~$360/month — $5,938 total interest
- 84 months: ~$321/month — $6,996 total interest
The jump from 36 to 84 months cuts the monthly payment by nearly half — but adds $4,090 in total interest. Always compare the total cost, not just the monthly payment, when evaluating loan terms.
How Extra Payments Reduce Interest
Extra monthly payments reduce your principal balance faster, which means every subsequent payment has less principal to charge interest on. The savings compound over time — even a modest extra $50 or $100 per month can meaningfully reduce total interest and payoff time.
On a $25,000 personal loan at 8.5% for 60 months (base payment ~$513/month): adding $100 extra per month cuts the payoff time from 60 months to approximately 46 months and saves roughly $900 in interest. Adding $200/month cuts the term to around 38 months and saves approximately $1,500. Use the extra payment field to experiment with scenarios before committing to a loan term.
Good vs. Bad Loan Interest Rates
What counts as a “good” rate depends on the loan type, your credit score, and current market conditions. General benchmarks:
- Personal loans: 8–12% is competitive for good credit (700+); 13–20% is average for fair credit; above 25% is expensive
- Auto loans (new): 5–8% is good for well-qualified buyers; 9–15% for fair credit
- Auto loans (used): 7–12% is typical for good credit
- Student loans (federal): fixed at rates set annually by Congress — typically 5–8%
- Credit card advances: 20–30%+ — nearly always the most expensive borrowing option
Your credit score is the single biggest factor in the rate you are offered. A 760+ score typically qualifies you for the best available rate; below 640, you may face rates that make borrowing expensive enough to reconsider.
APR vs. Interest Rate — What's the Difference?
The interest rate is the pure cost of borrowing — the percentage of the principal charged annually. APR (Annual Percentage Rate) includes the interest rate plus any lender fees rolled into the cost of the loan, such as origination fees (typically 1–5% of the loan amount for personal loans) or prepaid interest. Because APR captures all-in cost, it is the correct figure to use when comparing loan offers from different lenders.
This calculator uses the rate you enter as the interest rate, not APR. If your lender charges an origination fee, your effective cost is higher than the stated rate. To get a true picture, ask lenders for APR alongside their quoted rate. For most personal loans with origination fees of 1–3%, the APR is 0.5–1.5 percentage points higher than the nominal interest rate, depending on term length.
When to Consider Refinancing a Loan
Refinancing replaces your existing loan with a new one — ideally at a lower rate, shorter term, or both. It makes sense when: (1) your credit score has improved significantly since you took out the original loan; (2) market rates have dropped; or (3) you want to reduce monthly payments by extending the term (though this increases total interest). General rule: refinancing is worth pursuing if you can lower your rate by at least 1–2 percentage points and plan to stay in the loan long enough to recover any fees.
If you are managing multiple high-interest loans, debt consolidation — rolling them into a single lower-rate installment loan — can reduce both monthly payments and total interest. Compare total interest across both paths using this calculator before deciding. For home loans specifically, the mortgage calculator and credit card payoff calculator can help model your full debt picture.
Financial Disclaimer
This calculator is for educational and planning purposes only. Results are mathematical estimates based on the standard amortization formula and do not account for fees, prepayment penalties, variable rates, or other lender-specific terms. Actual loan costs will vary based on your lender, credit profile, and loan agreement. This tool does not constitute financial, credit, or legal advice. Consult a licensed financial advisor or lender for guidance specific to your situation.