Compound Interest vs Simple Interest

When it comes to growing your money or understanding loan costs, the type of interest makes a huge difference. Let's break down compound vs simple interest in plain terms.

What is Simple Interest?

Simple interest is calculated only on the original principal (your initial deposit or loan amount). It doesn't change over time.

Example:

You invest $1,000 at 5% simple interest for 3 years:
Interest = $1,000 × 0.05 × 3 = $150
Total after 3 years: $1,150

What is Compound Interest?

Compound interest is calculated on the principal plus any accumulated interest. Your interest earns interest — this is what makes it so powerful.

Where: A = final amount, P = principal, r = rate, n = compounds per year, t = years

Same Example with Compound Interest:

You invest $1,000 at 5% compounded annually for 3 years:
Year 1: $1,000 × 1.05 = $1,050
Year 2: $1,050 × 1.05 = $1,102.50
Year 3: $1,102.50 × 1.05 = $1,157.63

The Difference: $7.63 Extra

With compound interest, you earned $157.63 vs $150 with simple interest. That's 5% more earnings! And this gap grows dramatically over longer periods.

Comparison Over Time ($10,000 at 7%)

When Each Type is Used

Simple Interest is common in:

• Car loans
• Short-term personal loans
• Some bonds
• Interest-only mortgages

Compound Interest is common in:

• Savings accounts
• Investment accounts
• Credit cards (works against you!)
• Mortgages
• Student loans

Key Takeaways

• For savings: You want compound interest — the more frequent the compounding, the better
• For loans: Simple interest costs you less over time
• Time matters: Compound interest benefits grow exponentially with time
• Start early: The earlier you start investing with compound interest, the more dramatic the results