Simple Interest Calculator
Calculate simple interest on your savings and investments.
Need to calculate interest on a loan, deposit, or investment? Cready's simple interest calculator gives you the exact interest amount, maturity value, and step-by-step working - in seconds. Enter your principal, the annual interest rate, and the tenure in years, months, or days. The calculator instantly applies the SI formula (SI = P × R × T / 100) and shows your total interest and final amount, with a downloadable year-by-year breakdown.
Formula to Calculate Maturity
A = P (1 + r × t)
A = Total amount (maturity)
P = Principal amount = ₹ 50,000
r = Rate of interest = 8% = 0.0800
t = Tenure in years = 3
Simple Interest Formula
SI = P × R × T / 100
SI = Simple Interest
P = Principal amount
R = Rate of interest
T = Tenure in years
Your Calculation
Maturity Amount:
A = ₹ 50,000 × (1 + 8 × 3 / 100)
A = ₹ 50,000 × (1 + 0.2400)
A = ₹ 50,000 × 1.2400
A = ₹ 62,000
Simple Interest:
SI = ₹ 50,000 × 8 × 3 / 100
SI = ₹ 50,000 × 0.2400
SI = ₹ 12,000
Total Amount
₹62,000
What is a Simple Interest Calculator?
A simple interest calculator is a free online tool that computes the interest earned or owed on a principal amount at a fixed annual rate over a specified time period - without any compounding. You enter three values and get the result instantly:
- Principal (P) - the original amount invested or borrowed
- Rate of interest (R) - the annual interest rate in percentage
- Tenure (T) - the time period in years, months, or days
The calculator returns:
- Simple interest (SI) - the total interest earned or owed
- Maturity amount (A) - principal + interest at the end of the tenure
Cready's interest calculator also shows the full step-by-step calculation with actual numbers substituted into the formula - so you can see exactly how the result was derived, not just a black-box output.
Simple Interest Formula - How Is It Calculated?
There are two formulas used by the simple interest calculator:
Formula 1 - Simple Interest (SI)
Where:
- SI = Simple Interest (₹)
- P = Principal amount (₹)
- R = Annual rate of interest (%)
- T = Time period in years
Formula 2 - Maturity Amount (A)
Or equivalently: A = P + SI
How to Derive Rate of Interest from SI
If you know the principal, interest amount, and tenure but want to find the rate:
This is the rate of interest calculator formula - useful when you've received an interest offer and want to verify the actual annual rate.
How to Find the Principal from SI
How to Find the Time Period from SI
Simple Interest Calculation - Worked Examples
Example 1 - Basic SI calculation
₹50,000 deposited at 8% p.a. for 3 years.
SI = 50,000 × 8 × 3 / 100 = ₹12,000
A = 50,000 + 12,000 = ₹62,000
Example 2 - Calculate rate of interest
₹1,00,000 grows to ₹1,15,000 in 2 years.
SI = ₹15,000
R = (15,000 × 100) / (1,00,000 × 2) = 7.5% p.a.
Example 3 - Monthly tenure
₹30,000 at 10% p.a. for 6 months (0.5 years).
SI = 30,000 × 10 × 0.5 / 100 = ₹1,500
A = 30,000 + 1,500 = ₹31,500
Example 4 - Personal loan (flat rate)
₹2,00,000 personal loan at 12% flat for 24 months (2 years).
SI = 2,00,000 × 12 × 2 / 100 = ₹48,000
Total repayable = ₹2,48,000
Monthly flat EMI = ₹2,48,000 ÷ 24 = ₹10,333/month
Note: Most personal loans in India use reducing balance (not flat rate) for EMI calculation. See the comparison in "Is Simple Interest Better Than Compound Interest?" below.
How to Use Cready's Simple Interest Calculator
- Enter the principal amount - the amount you're investing or borrowing (₹0 to ₹1,00,00,000)
- Set the interest rate - the annual rate in % (0% to 40%)
- Select the tenure - in years (1–50), months, or days
- View results instantly - simple interest earned, maturity amount, and full formula working
- Download the yearly breakdown - use the download button for a year-by-year table
The calculator automatically updates results as you adjust any slider or input value - no "calculate" button needed.
Where is Simple Interest Used in India?
Understanding where SI applies helps you use this calculator correctly and spot the right situations:
Loans where flat (simple) interest is quoted:
- Some personal loan offers from smaller NBFCs or moneylenders quote a "flat rate" - which is simple interest on the original principal throughout the tenure, not reducing balance. Always verify which method applies before accepting.
- Gold loans from some lenders may use simple interest on the outstanding principal
- Short-term loans or bridging finance sometimes use SI for tenures under 6 months
Savings schemes and deposits:
- Post Office Savings Account: 4% p.a., simple interest applied annually
- Kisan Vikas Patra (KVP): while the scheme compounds annually, individual year returns can be understood via SI for quick estimation - try our Kisan Vikas Patra calculator
- Short-tenure FDs and RDs may use simple interest for partial-year calculations
Education and general financial literacy:
- NCERT curriculum - simple interest is taught in classes 7 and 8 as the foundation of financial mathematics
- Competitive exam preparation (GMAT, CAT, bank PO, SSC) - SI and CI problems are standard sections
Government scheme interest calculations:
- National Savings Certificate (NSC) calculations for partial years
- Senior Citizen Savings Scheme (SCSS) quarterly interest payouts (effectively SI per quarter)
Is Simple Interest Better Than Compound Interest?
The answer depends on whether you're borrowing or investing:
If you're borrowing: Simple interest (flat rate) means you pay interest only on the original principal, which stays constant. This is cheaper than a reducing balance loan at the same nominal rate - but only if the flat rate itself is lower. A 12% flat rate personal loan is actually more expensive than a 16% reducing balance loan over a 2-year tenure. Use the calculator to verify.
If you're investing: Compound interest is almost always better. The interest on previous interest creates exponential growth that simple interest cannot match over longer tenures. Compare with our compound interest FD calculator, or see how PPF compounds annually at 7.1% tax-free.
Benefits of Using the Simple Interest Calculator
- Instant, Error-Free Results - Manual SI calculation for multi-year tenures is prone to arithmetic errors. The calculator eliminates this instantly, with step-by-step working shown alongside the result.
- Three Tenure Formats - Unlike most SI calculators that only accept years, Cready's supports years, months, and days - useful for short-term loans, partial-year FD calculations, or daily interest products.
- Reverse Calculations - Use the formula tools to work backwards: if you know SI earned and the principal and time, calculate the rate of interest. Useful for verifying whether a lender's quoted rate matches what you'll actually pay.
- Downloadable Yearly Breakdown - The year-by-year table shows your interest and total amount at the end of each year - useful for multi-year financial planning.
- No Registration, Instant, Free - No login required. Results update in real time as you adjust any input.
Frequently Asked Questions
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