Loan Comparison Calculator

Compare two different loans side-by-side to find the lowest interest rates and payments.

Status: Algorithmic Audit (CPA Review Pending)
Jurisdiction: United States (IRS & SSA Standards)
Tax Year / Constants: 2026 Statutory Limits
Data Privacy: 100% Client-Side In-Browser

The Mathematical Formula

Lifetime Finance Charge = (Monthly Payment × n) - Principal ; Net Cost Difference = Finance Charge A - Finance Charge B

Variable & Parameter Definitions

  • Monthly Payment The calculated monthly principal and interest installment for each loan option.
  • Finance Charge Total dollar amount of interest paid over the entire life of the loan.
  • Net Cost Difference The total cash savings realized by selecting the lower-cost financing package.

Real-World Worked Scenario: Comparing 30-Year 6.5% vs 15-Year 5.75% on $350,000

A borrower compares a 30-year loan at 6.50% versus a 15-year loan at 5.75% on a $350,000 borrowing balance.

  1. Option A (30-Year at 6.50%): Monthly Payment = $2,212.24 ; Total Payments = $796,406 ; Total Interest = $446,406.
  2. Option B (15-Year at 5.75%): Monthly Payment = $2,906.59 ; Total Payments = $523,186 ; Total Interest = $173,186.
  3. Monthly Payment Difference: Option B requires +$694.35 more cash flow each month.
  4. Lifetime Net Savings: $446,406 - $173,186 = $273,220 saved in pure interest under Option B.
Key Financial Takeaway: Taking on a higher monthly payment on a 15-year loan saves hundreds of thousands of dollars in interest and builds equity twice as fast.

Strategic Insights & Pitfalls to Avoid

  • ✓ Evaluate Cash Flow Flexibility: A 30-year loan allows you to pay like a 15-year loan optionally, maintaining safety if financial hardship occurs.
  • ✓ Closing Costs Matter: Always compare the Loan Estimate forms line-by-line for differences in origination, appraisal, and title charges.
  • ✓ APR vs Interest Rate: When compare loans with different fees, compare APR rather than just the nominal note rate.

Frequently Asked Questions

Why is the interest rate on a 15-year mortgage usually lower than a 30-year mortgage?

Lenders face lower inflation risk and default duration risk over 15 years, allowing them to offer lower interest rates (typically 0.5% to 0.75% lower).

Should I choose the lowest payment or the lowest total interest?

Choose the lowest payment if cash flow stability is your primary concern; choose lowest total interest if maximizing multi-decade net worth is your goal.

What is a Loan Estimate?

A standardized 3-page disclosure form that lenders must provide within 3 business days of application detailing exact loan terms, interest rates, and closing costs.

Related Decision Calculators

Loan & Mortgage Calculator Calculate monthly loan payments, interest payments, and amortizat... Loan Refinance Calculator Determine if refinancing your loan will save you money on interes... APR Calculator Calculate the true Annual Percentage Rate (APR) of a loan, includ... Fixed vs Adjustable Rate Calculator Compare fixed-rate mortgages with adjustable-rate mortgages (ARM)...