Simple Interest Calculator

💰 How This Calculator Works

Calculates interest without compounding — used for short-term loans, bonds, and simple savings accounts. Interest accrues only on the original principal.

🔢 Worked Examples

• $5,000 at 3% for 2 years = $300 interest
• $10,000 at 5% for 6 months = $250
• £2,000 at 4.5% for 90 days = £22.19

📋 Common Use Cases

Interest calculators cover compound interest, simple interest, and time-value-of-money concepts. Understanding the difference between nominal and effective rates — and how compounding frequency affects returns — can mean thousands of dollars difference over a savings or investment horizon.

• Comparing savings account yields by compounding frequency
• Computing the true annual rate from a monthly-quoted rate
• Projecting investment growth under different return assumptions
• Understanding the "Rule of 72" for doubling time

💡 Did You Know?

Daily compounding at 5% annual grows money to 5.127% effective rate. Compounding matters more the longer you invest — the difference between annual and daily compounding on a 30-year $10,000 investment is over $1,500.

⚠️ Common Mistake

Using days without adjusting the rate — for daily simple interest, divide the annual rate by 365 (or 360 for some financial instruments).