How to Calculate Loan Interest (2023)

On February 25, 2026  By newsroom   Topic: Debt Advice

Understanding how loan interest works can save you money and help you manage repayments effectively. Here's a breakdown:


1. Simple Interest Calculation \uddee

  • Formula: Principal (P) x Interest Rate (R) x Time (T) ô7 100
  • Example: A $10,000 loan at 5% interest for 3 years:

    • Interest = \( 10,000 \times 5 \times 3 \div 100 = \$1,500 \)
  • Key Point: Simple interest doesn't compound, so it's straightforward to calculate.


2. Amortization Loans

  • Used for mortgages, auto loans, and student loans.
  • Formula:
  • Interest Due = Remaining Loan Balance \u00d7 (Annual Interest Rate ô7 12)
  • Principal Payment = Monthly Payment \u2212 Interest Due

  • Example:

  • Loan: $400,000 at 8% interest, Monthly Payment: $2,935
  • First Month:
    • Interest = \( 400,000 \times 0.08 \div 12 = \$2,666.67 \)
    • Principal = \( 2,935 \u2212 2,666.67 = \$268.33 \)

3. Loan Interest vs. APR

  • Interest Rate: Cost of borrowing based only on the principal.
  • APR (Annual Percentage Rate): Includes interest, fees, and other costs.
  • APR provides a complete picture of loan expenses and is better for comparing loan options.

4. How Interest Rates Are Determined

  • Factors:
  • Market Conditions: Fed rates, treasury bonds, and bank policies.
  • Borrower Profile: Credit score, income, and debt-to-income ratio (DTI).
  • Loan Type:
    • Secured loans (e.g., auto loans) have lower rates due to collateral.
    • Unsecured loans (e.g., personal loans) typically have higher rates.

5. Tips to Get the Best Rates

  • Improve Your Credit Score:
  • Resolve past-due debts.
  • Keep credit utilization under 30%.
  • Check for and dispute credit report errors.

  • Shop Around:

  • Compare multiple lenders using loan comparison tools.

  • Opt for Automatic Payments:

  • Many lenders offer discounts for setting up auto-pay.

  • Shorten Your Loan Term:

  • Shorter terms usually result in lower interest rates.

  • Consider a Co-Signer:

  • A co-signer with good credit can help secure better terms.

  • Improve Debt-to-Income Ratio:

  • Pay down existing debts to qualify for lower rates.

FAQs on Loan Interest

  • Better to Pay Interest or Principal First?
  • Prioritize paying the principal to reduce the amount generating interest.

  • Daily Interest Calculation:

  • Formula: \( \text{Annual Rate} \div 365 \times \text{Principal} \)
  • Example: A $10,000 loan at 10% annual rate:
    • Daily Interest = \( 0.10 \div 365 \times 10,000 = \$2.73 \).

Bottom Line

  • Loan interest affects your total repayment significantly.
  • Use online calculators to estimate costs and explore scenarios.
  • Pay off loans faster to save on interest - unless there are prepayment penalties.
  • Always compare lenders to ensure you're getting the best deal.

Smart borrowing = smart saving!


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