What is Simple Interest and the formula?

Simple Interest is calculated only on the principal amount, not on accumulated interest. Formula: SI = (P × R × T) / 100, where P is principal, R is annual rate (%), and T is time (years).

How is Simple Interest different from Compound Interest?

Simple Interest is calculated only on principal. Compound Interest is calculated on principal + accumulated interest. Compound Interest yields higher returns over longer periods.

Can I calculate SI for months or days?

Yes. For months: SI = (P × R × M) / 1200. For days: SI = (P × R × D) / 36500 (for 365-day year). This calculator supports all three.

Who uses Simple Interest?

Simple Interest is used for short-term loans (personal loans, overdrafts), bonds, short-term deposits, and some traditional savings schemes.

How do I calculate the principal if I know SI and rate?

Rearranging the formula: P = (SI × 100) / (R × T). For example, if SI is ₹5,000 at 10% for 2 years, then P = (5,000 × 100) / (10 × 2) = ₹25,000.

Simple Interest Calculator

Calculate simple interest with precision across Years, Months, or Days. Automatic leap year detection ensures maximum accuracy.

Investment Details

Quick-Start Examples

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Maturity Details

Interest Accrued

₹1,35,000

earned at 9% p.a.

Principal

₹5,00,000

Maturity Value

₹6,35,000

Daily Accrual

₹123.29

Understanding Your Simple Interest

Simple Interest is calculated only on the principal amount throughout the tenure. Unlike compound interest, it doesn't earn interest on interest.

Principal Amount: ₹5,00,000 - Your initial investment

Interest Earned: ₹1,35,000 - Money earned at 9% p.a. for 3 year(s)

Maturity Amount: ₹6,35,000 - Total amount you'll receive (Principal + Interest)

Key Insights

Return Multiple: 1.27x - Your money will grow by 27.0%

Interest Rate Comparison: At 9% p.a., you earn ₹45,000 per year

Daily Earnings: ₹123.29 per day - Or ₹3,698.7 per month on average

Disclaimer: This calculation assumes constant interest rates and regular calculations. Actual amounts may vary based on lender terms and conditions.

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✅ Simple Interest Calculator

📥 INPUTS (Assumptions):

• Principal Amount: ₹5,00,000

• Annual Interest Rate: 9%

• Tenure: 3 Year(s)

📤 RESULTS (Outputs):

• Total Maturity Value: ₹6,35,000

• Interest Accrued: ₹1,35,000

• Daily Interest Accrual: ₹123.29

🔗 Calculated using CalculoX

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Growth Visualization

SI Breakup

Principal₹5,00,000

Interest Accrued₹1,35,000

What is Simple Interest?

Simple Interest (SI) is interest calculated only on the principal amount throughout the entire tenure, without any compounding. Unlike compound interest, simple interest does not earn interest on previously accumulated interest. The formula for simple interest is: SI = (P × R × T) / 100, where P is the principal amount, R is the annual interest rate (%), and T is the time period in years.

Simple interest is commonly used in personal loans, auto loans, home loans, and government savings schemes. Because SI doesn't compound, the total amount you earn or pay is proportional to the time period, making it predictable and easy to calculate for short-term investments and loans.

Simple Interest vs Compound Interest: Key Differences

Aspect	Simple Interest	Compound Interest
Calculation Basis	Only on principal	On principal + earned interest
Formula	SI = (P × R × T) / 100	A = P(1 + R/100)^T
Interest Growth	Linear (straight line)	Exponential (accelerating)
Total Returns (5 yrs @ 10%)	₹1,00,000 → ₹1,50,000	₹1,00,000 → ₹1,61,051
Common Uses	Personal loans, car loans, home loans	FDs, savings accounts, investments
Predictability	Easy to calculate, predictable	More complex, accelerating returns

Key Insight: Over longer periods, compound interest significantly outpaces simple interest. For investments, compound interest works in your favor. For loans, simple interest is more borrower-friendly than compound interest.

How to Calculate Simple Interest in 5 Steps?

1.
Gather the Required Information: You need three pieces of data: Principal Amount (P) — the initial amount invested or borrowed; Annual Interest Rate (R) — the percentage charged per year; Time Period (T) — how long the money is invested or borrowed (in years, months, or days).
2.
Identify the Time Period Type: Determine if your time period is in years, months, or days. If in years, use T as-is. If in months, divide by 12. If in days, divide by 365 (or 366 for leap years). This ensures the calculation aligns with the annual interest rate.
3.
Apply the Simple Interest Formula: Use the formula: SI = (P × R × T) / 100. For example, if Principal is ₹1,00,000, Rate is 8% p.a., and Time is 3 years: SI = (100,000 × 8 × 3) / 100 = ₹24,000.
4.
Calculate the Maturity Amount: Add the interest earned to the principal to get the total amount: Maturity Amount = Principal + SI. In our example: ₹1,00,000 + ₹24,000 = ₹1,24,000 (the total you receive).
5.
Verify Using the Complete Formula: Alternatively, calculate maturity in one step using: A = P × (1 + R×T/100). This combines principal and interest into one calculation for convenience.

Real Example: You invest ₹50,000 in a savings scheme offering 7% simple interest for 2 years. SI = (50,000 × 7 × 2) / 100 = ₹7,000. Maturity amount = ₹50,000 + ₹7,000 = ₹57,000 (your total after 2 years).

Frequently Asked Questions

What is Simple Interest?

Simple Interest (SI) is interest calculated only on the principal amount, without compounding. Unlike compound interest, SI doesn't earn interest on previously earned interest. Formula: SI = (P × R × T) / 100, where P is principal, R is annual rate (%), and T is time period.

What are the three tenure types and when to use them?

Years: Most common for long-term investments and traditional loans (mortgages, vehicle loans).
Months: Used for medium-term arrangements like personal loans, peer-to-peer lending, or short-term bonds.
Days: Essential for banks calculating overdraft charges, short-term credit lines, bond accruals, or any daily interest scenario requiring precision.

How are the formulas adjusted for different time periods?

Years: SI = (P × R × Years) / 100.
Months: SI = (P × R × Months) / 1200. We divide by 1200 because 1200 = 100 × 12.
Days: SI = (P × R × Days) / (100 × DaysInYear). This calculator automatically detects leap years, using 366 days during leap years and 365 days otherwise for maximum accuracy.

What is daily interest accrual and why is it useful?

Daily accrual shows how much interest accumulates per day: (P × R) / DaysInYear. For users calculating short-term commercial returns or friendly loans, this provides practical insight into daily interest growth. For example, on ₹1 lakh at 8% p.a., daily accrual is roughly ₹21.92 per day, making it easy to estimate interest for any number of days.

When is Simple Interest used vs. Compound Interest?

Simple Interest: Used for most personal loans, auto loans, home loans, and government savings schemes like Sukanya Samriddhi.
Compound Interest: Used for Fixed Deposits, savings accounts, mutual funds, and investments where interest is reinvested. Over the same period, CI yields significantly more interest than SI, so always verify which method your financial institution uses.

How does leap year affect daily interest calculations?

During leap years (366 days instead of 365), interest accrual is slightly lower since the same annual rate is spread across one additional day. This calculator automatically detects leap years when you use the Days tenure type, ensuring your daily interest calculations are accurate down to the penny. This is critical for banks and financial institutions that must maintain regulatory precision.

Simple Interest vs Compound Interest — Formula and Examples

Simple Interest (SI) is calculated only on the original principal amount throughout the entire loan or investment tenure. The interest does not compound — it does not earn further interest on itself. SI is used in short-term personal loans, overdraft facilities, government bonds, post-office savings schemes, and some traditional deposit products. It is transparent and easy to verify, which is why regulatory bodies often mandate SI disclosure alongside compound interest figures.

Simple Interest Formula

SI = (P × R × T) ÷ 100

Where P is the principal amount, R is the annual interest rate (%), and T is the time in years. For months: T = M ÷ 12. For days: T = D ÷ 365 (or 366 for leap years). Total amount at maturity = P + SI.

Worked Example

You take a personal loan of ₹1,50,000 at 9% per annum for 2 years and 6 months (2.5 years):

SI = (1,50,000 × 9 × 2.5) ÷ 100 = ₹33,750
Total repayment = ₹1,50,000 + ₹33,750 = ₹1,83,750
Monthly payment = ₹1,83,750 ÷ 30 months = ₹6,125/month

Had this been compound interest (compounded monthly), the total interest on the same loan would be ₹36,211 — about ₹2,461 more. The difference grows larger with longer tenures, which is why banks typically use compound interest for home loans but simple interest for certain overdraft products.

Period	Interest Earned (₹)	Total Amount (₹)
Year 1	₹45,000	₹5,45,000
Year 2	₹90,000	₹5,90,000
Year 3	₹1,35,000	₹6,35,000

Period	Interest Earned (₹)	Total Amount (₹)
Year 1	₹45,000	₹5,45,000
Year 2	₹90,000	₹5,90,000
Year 3	₹1,35,000	₹6,35,000

Simple Interest Calculator

Investment Details

Quick-Start Examples

Short-Term Loan

Education Fund

Business Investment

Formula Reference

Maturity Details

Understanding Your Simple Interest

Key Insights

Growth Visualization

SI Breakup

What is Simple Interest?

Simple Interest vs Compound Interest: Key Differences

How to Calculate Simple Interest in 5 Steps?

Frequently Asked Questions

Simple Interest vs Compound Interest — Formula and Examples

Simple Interest Formula

Worked Example

Simple Interest Calculator

Investment Details

Quick-Start Examples

Short-Term Loan

Education Fund

Business Investment

Formula Reference

Maturity Details

Understanding Your Simple Interest

Key Insights

Interest Projection Schedule

Growth Visualization

SI Breakup

What is Simple Interest?

Simple Interest vs Compound Interest: Key Differences

How to Calculate Simple Interest in 5 Steps?

Frequently Asked Questions

Interest Projection Schedule