Simple Interest Calculator
You need a quick, honest number — here's what you actually earn (or owe) without the compounding.
✓ Formula verified June 2026✓ Source: Investopedia
Live Rates
Live rates
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Initial deposit or loan amount
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Enter your values to see results
Worked Examples
3-year savings deposit
Principal: $10,000 · Rate: 5% · Time: 3 years → SI = $1,500 · Total: $11,500. Simple interest is linear — each year earns the same $500.
Short-term loan
Principal: $5,000 · Rate: 8% · Time: 6 months (0.5 yr) → SI = $200 · Total: $5,200. Fractions of a year work directly in the formula.
Long-term bond
Principal: $50,000 · Rate: 3.5% · Time: 10 years → SI = $17,500 · Total: $67,500. Over 10 years, 3.5% simple interest adds 35% of the original principal.
Frequently Asked Questions
~4 min readWhat is the difference between simple and compound interest?▾
Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus any previously accumulated interest. Over time, compound interest grows exponentially while simple interest grows linearly. For short time periods or low rates the difference is small, but over decades it becomes significant.
Does simple interest apply to loans or savings?▾
Both. Car loans, short-term personal loans, and some bonds use simple interest. Savings accounts and mortgages typically use compound interest. Always check the product terms — "5% annual interest" can mean different things depending on whether it is simple or compounded.
How do I convert a monthly rate to annual?▾
Multiply the monthly rate by 12. For example, a 0.5% monthly rate is 6% annual under simple interest. Note that this conversion is not valid for compound interest, where the correct conversion is (1 + monthly rate)^12 - 1.
Can I enter fractions of a year?▾
Yes. Enter 0.5 for 6 months, 0.25 for a quarter, or any decimal value. The formula SI = P × r × t handles any positive value of t.
What is the formula used?▾
SI = P × r × t, where P is the principal, r is the annual interest rate as a decimal (e.g. 5% = 0.05), and t is the time in years. Total amount A = P + SI.
Is the interest taxable?▾
In most countries, interest income is taxable. The amount and rate depend on your local tax laws. This calculator shows gross interest before any deductions. Consult a tax advisor for your specific situation.
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For informational purposes only. Not financial advice. Formula last verified June 2026. See our Privacy Policy for data handling.