Loan Comparison Calculator
Compare two loan offers side by side to see which saves you more money.
Results
Visualization
How It Works
The Loan Comparison Calculator helps you evaluate two competing loan offers by calculating monthly payments and total costs for each, then showing you which loan saves you the most money. This is essential when comparing mortgages, auto loans, personal loans, or refinancing options, where small differences in interest rates or terms can mean thousands of dollars in savings or extra costs over the life of the loan. This tool is designed for both quick estimates and detailed planning scenarios. Results update instantly as you adjust inputs, making it easy to compare different approaches and understand how each variable affects the outcome. For best accuracy, use precise measurements rather than rough estimates, and consider running multiple scenarios to establish a realistic range of expected results.
The Formula
Variables
- P (Loan Amount) — The principal amount you're borrowing, in dollars. This is the same for both loans in the comparison.
- r (Interest Rate) — The annual percentage rate (APR) charged on the loan, expressed as a percentage. This varies between Loan A and Loan B and directly affects your monthly payment.
- n (Loan Term) — The total length of the loan in months. A 30-year mortgage equals 360 months; a 5-year auto loan equals 60 months. Longer terms mean lower monthly payments but higher total interest paid.
- Monthly Payment — The fixed amount you pay each month toward principal and interest. The calculator determines this based on the loan amount, rate, and term.
- Total Cost — The sum of all monthly payments over the life of the loan—this reveals the true cost of borrowing, including all interest paid.
Worked Example
Let's say you're comparing two mortgage offers for a $300,000 home loan. Loan A offers 6.5% interest over 30 years (360 months), while Loan B offers 6.0% interest over 25 years (300 months). For Loan A: the monthly rate is 6.5% ÷ 12 = 0.542%, and using the payment formula, your monthly payment works out to approximately $1,896. Over 360 months, your total cost is $1,896 × 360 = $682,560. For Loan B: the monthly rate is 6.0% ÷ 12 = 0.5%, giving you a monthly payment of approximately $1,799. Over 300 months, your total cost is $1,799 × 300 = $539,700. By choosing Loan B, you save $682,560 − $539,700 = $142,860 in total costs, even though your monthly payment is only $97 lower—the advantage comes from paying off the loan 5 years faster.
Practical Tips
- Don't focus only on the monthly payment—compare the total cost instead. A loan with a lower monthly payment might have a longer term, meaning you pay far more interest overall. Always look at the 'Total Cost' output to see the true price of each loan.
- Watch out for the relationship between interest rate and term: a lower rate doesn't always mean lower total costs if the term is significantly longer. Use this calculator to test different combinations and find your actual break-even point.
- Consider your cash flow situation alongside the math: if you can afford the higher monthly payment of a shorter-term loan, you'll save substantial money in interest, but make sure you have adequate emergency savings before stretching your budget.
- Factor in other loan costs that might not be reflected here, such as origination fees, closing costs, mortgage insurance (PMI), or prepayment penalties. Add these to the total cost for a complete picture of what each loan truly costs.
- If one loan has a variable interest rate and the other is fixed, remember that this calculator shows today's numbers—your actual costs could be higher if rates adjust upward. Use this as a baseline comparison and apply a buffer for potential rate increases.
Frequently Asked Questions
Why does a lower interest rate sometimes result in higher monthly payments?
It doesn't—a lower interest rate always produces lower monthly payments if the loan amount and term are the same. However, if Loan B's lower rate comes with a much shorter term (like 15 years instead of 30), the monthly payment could be higher despite the better rate. The shorter term is the reason, not the lower rate. This is why comparing both monthly payment and total cost matters.
Should I always choose the loan with the lowest monthly payment?
No. The lowest monthly payment typically means a longer loan term, which means you'll pay much more total interest. For example, a 30-year mortgage will have lower monthly payments than a 15-year mortgage at the same rate, but you'll pay nearly twice as much in total interest. Choose the lowest monthly payment only if affordability is your primary concern and you cannot qualify for a shorter term.
What's the difference between APR and interest rate?
The interest rate is the percentage charged on your loan balance, while the Annual Percentage Rate (APR) includes the interest rate plus other costs like origination fees, closing costs, and insurance. For this calculator, use the APR if available, as it gives a more complete picture of the true cost. Lenders are required to disclose APR on loan documents.
Can I use this calculator to compare a fixed-rate and adjustable-rate loan?
Yes, but understand the limitations. This calculator assumes interest rates remain constant, so it accurately reflects a fixed-rate loan but only shows the initial rate for an adjustable-rate loan. For ARM comparison, enter the current rate and estimate what rates might be after adjustments, then run the calculator multiple times with different scenarios to see the range of possible outcomes.
Why might I choose a loan with higher total costs?
Several legitimate reasons exist: lower monthly payments might fit your current budget better, you might plan to sell or refinance before the loan matures (making early payoff irrelevant), or you might have better investment returns than the loan's interest rate, making the cheaper loan mathematically suboptimal but practically worthwhile. Always consider your personal financial situation, not just the numbers.
Sources
- Consumer Financial Protection Bureau (CFPB) — Loan Comparison Tools
- Federal Reserve — Understanding Interest Rates and APR
- U.S. Department of Housing and Urban Development (HUD) — Mortgage Comparisons