Free simple vs compound interest calculator. Compare both in your local currency. Works worldwide.
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⚠️ Estimates only. Not financial advice. Consult a licensed professional.
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Simple interest calculates the cost of borrowing (or the return on savings) based only on the original principal amount — it does not charge interest on previously accumulated interest. While compound interest governs most modern financial products, simple interest remains relevant in several specific contexts and serves as an important educational foundation for understanding all types of interest calculations.
Interest (I) = Principal (P) × Rate (R) × Time (T)
Total Amount (A) = P + I
Where:
P = Original principal amount
R = Annual interest rate (as decimal: 10% = 0.10)
T = Time in years
Example: ₹50,000 at 8% for 18 months (1.5 years)
I = ₹50,000 × 0.08 × 1.5 = ₹6,000
A = ₹56,000
For very short periods (under 1 year), simple and compound interest produce nearly identical results. The difference becomes significant over longer periods and at higher interest rates. Here is a direct comparison at 10% interest rate:
₹1,00,000 at 10% annual:
1 year: Simple = ₹10,000 interest | Compound (annual) = ₹10,000 interest (same)
3 years: Simple = ₹30,000 interest | Compound (annual) = ₹33,100 interest (+₹3,100)
5 years: Simple = ₹50,000 interest | Compound (annual) = ₹61,051 interest (+₹11,051)
5 years: Simple = ₹50,000 interest | Compound (quarterly) = ₹63,862 interest (+₹13,862)
Informal and peer-to-peer lending: Most family loans, employer advances, and informal credit use simple interest for clarity and ease of calculation. Both parties can understand and verify the calculation without any financial knowledge.
Short-term bridge loans and overdrafts: Some bank overdraft facilities and short-term business loans calculate interest on daily outstanding balances using a simple daily interest rate — effectively simple interest applied on a daily basis.
Post Office savings schemes: Some Post Office time deposit products quote returns based on simple interest principles for marketing clarity, though the actual calculation may use quarterly compounding.
Chit funds: Monthly rotating savings clubs (chit funds) use simple interest for bid discount calculations and distribution of surplus funds among members.
Two-wheeler loans, used car loans, and consumer durable loans in India often use a "flat rate" structure that functions similarly to simple interest — charging a fixed percentage on the original principal throughout the tenure, regardless of repayment. This is why flat rate loans cost nearly double the equivalent APR (reducing balance) loan at the same stated percentage.
Use the APR Converter tool on this site to convert any flat rate to its true APR equivalent. This allows fair comparison between flat-rate and reducing-balance offers from different lenders.
In microfinance and rural lending contexts, simple interest is widely used for its transparency and ease of verification by borrowers with limited financial literacy. SHG (Self-Help Group) loans, NBFC-MFI (Microfinance Institutions) loans, and Kisan Credit Card interest calculations are often explained using simple interest principles even when the actual calculation may involve daily reducing balance methods. Understanding simple interest gives rural borrowers a foundation to verify whether they are being charged fairly.
To verify if your lender is using simple interest or reducing balance, take your last month's interest payment, divide by your outstanding balance, and multiply by 12. If this equals your quoted annual rate, it is reducing balance (correct and fair). If the result is significantly lower than your quoted rate, the lender may be using a hybrid or flat rate method. This test takes 30 seconds and protects you from being overcharged.