General Finance
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Simple Interest Calculator
Work out interest on a non-compounding loan or deposit quickly. Adjust any input below and your results update instantly.
Understanding simple interest
The concept, the motivation, and what to watch out for.
What makes interest "simple"?
Simple interest is calculated only on the original principal — the same rupee amount is added every year, regardless of how long the money has been growing. Unlike compound interest, it never earns interest on interest already added.
That makes it easy to calculate by hand, and it's still used for some short-term loans and older-style instruments — but it also means it grows meaningfully slower than compounding over longer periods.
Interest is always on the same base
Every year's interest is calculated on the original principal alone — the amount never grows to include interest already earned, unlike compounding.
Growth is a straight line, not a curve
Because the same rupee amount is added every year, a simple interest balance grows linearly over time, while a compounding balance curves upward.
How this calculator helps
Enter your principal, rate, and time period — see your simple interest, and exactly how much more the same numbers would earn if compounded instead.
Calculate your simple interest
Fill in the starred fields on the left — your results update instantly on the right.
Your details
≈ ₹1.00 L
e.g. ₹1,00,000
e.g. 8% a year
e.g. 5 years
How these compare
vs. typical India long-term ranges
Interest rate: 8%
Typical India loan/deposit range: 6–10%
These are example numbers. Edit any input on the left to see your own.
Your simple interest is
₹40,000
over 5 years at 8%
Total amount
₹1.40 L
Compounding would earn
₹46,933
Simple vs. compound interest growth
Simple interestCompound interest
Same principal, rate, and years — simple interest grows in a straight line, while compounding curves upward as it starts earning interest on its own interest.
Year-by-year breakdown
Shows how far ahead compounding would be at each point, for the same principal and rate.
YearSimple interest valueCompound interest valueStatus
0₹1.00 L₹1.00 L
Start
Compounding would be ahead by 0% at year 0
1₹1.08 L₹1.08 L
+0%
Compounding would be ahead by 0% at year 1
2₹1.16 L₹1.17 L
+1%
Compounding would be ahead by 1% at year 2
3₹1.24 L₹1.26 L
+2%
Compounding would be ahead by 2% at year 3
4₹1.32 L₹1.36 L
+3%
Compounding would be ahead by 3% at year 4
5₹1.40 L₹1.47 L
+5%
Compounding would be ahead by 5% at year 5
Compare scenarios
See how a higher rate or a longer period changes your interest.
Your plan
8% · 5y
₹40,000
Simple interest
Baseline
Rate 10%
10% · 5y
₹50,000
Simple interest
+₹10,000
10 years
8% · 10y
₹80,000
Simple interest
+₹40,000
Worked example, using your numbers
A step-by-step walkthrough of how your simple interest is calculated.
Step 1 · Simple interest
₹1.00 L at 8% for 5 years becomes
₹40,000
Step 2 · Total amount
Adding that interest back to your principal gives
₹1.40 L
Step 3 · If compounded instead
The same numbers, compounded annually, would instead reach
₹1.47 L
✓
Your ₹1.00 L earns ₹40,000 in simple interest — ₹6,933 less than compounding would earn.
Personalised insights
What your numbers reveal, and what changing them would do.
Your ₹1.00 L at 8% for 5 years earns ₹40,000 in simple interest
That brings your total amount to ₹1.40 L — the same rupee amount added every year.
Compounded annually instead, the same numbers would earn ₹46,933
That's ₹6,933 more than simple interest — the gap that comes purely from earning interest on interest already added.
A 10% rate would raise your simple interest to ₹50,000
Even without changing your principal or time period, a higher rate directly raises simple interest, since it scales linearly with rate.
Extending to 10 years would raise it to ₹80,000
Simple interest keeps growing by the same rupee amount every additional year — no acceleration, unlike compounding.
How this is calculated
Every step of the math behind your result, shown in the open.
Your simple interest
P = principal, R = annual rate (%), T = years, SI = simple interest
The principal (P) is multiplied by the rate (R) and the number of years (T) — since the base never changes, this grows by the same rupee amount every year.
Example: ₹1.00 L × 8% × 5 years → ₹40,000 simple interest
Your total amount
P = principal, SI = simple interest, A = total amount
Adding the simple interest back to the principal gives the total amount at the end of the period.
Example: ₹1.00 L + ₹40,000 → ₹1.40 L total amount
The compounding alternative
P = principal, R = annual rate (%), T = years, A_compound = value if compounded annually
For comparison, the same principal, rate, and years under annual compounding — each year's interest is added to a growing base, not just the original principal.
Example: ₹1.00 L compounding at 8%/yr for 5 years → ₹1.47 L
Assumptions
- Interest is calculated on whole years only, at a constant rate throughout.
- The compounding comparison assumes annual compounding, purely as a reference point.
- Figures are indicative and pre-tax — not financial advice.
Did you know?
A few facts behind simple interest.
Linear
Simple interest never accelerates
A simple interest balance grows by the exact same rupee amount every year — no matter how long you wait, it never picks up speed the way compounding does.
72
The Rule of 72 doesn't apply here
That popular shortcut for estimating doubling time is built entirely around compounding — a simple interest balance takes a fixed, easily-calculated 100/R years to double instead.
History
Simple interest predates cheap computation
Long before calculators and spreadsheets, simple interest was the practical choice for everyday lending — easy to compute by hand, with none of compounding's exponential bookkeeping.
Short
Still common for short-term borrowing
Some short-tenure personal loans and late-payment penalty charges still use simple interest, since the difference from compounding is small over a few months.
Frequently asked questions
Straight answers to the questions we hear most about simple interest.
What is simple interest?
Interest calculated only on the original principal, at a fixed rate, for a fixed time period — the same rupee amount is added every year, and it's never added back into the base that earns further interest.
How is this different from compound interest?
Compound interest is calculated on the principal plus all interest already earned, so the base grows every year and returns accelerate over time. Simple interest always uses the original, unchanging principal.
Where is simple interest actually used?
Some short-term personal loans, certain bonds, and many everyday quick-interest calculations (like penalty interest on a late payment) use simple interest, largely because it's straightforward to calculate without compounding tables.
Does the time period have to be in whole years?
No — the formula works the same way for any time period (months, days), as long as the rate is adjusted to match. This calculator assumes whole years for simplicity.
Is simple interest better for borrowers or lenders?
Generally better for borrowers, since interest doesn't compound on itself — a loan charged simple interest costs less over time than the same rate compounded. For deposits, the reverse is true: a saver typically earns more from compounding.
Is this financial advice?
No. This tool provides indicative estimates based on your assumptions. Consult a certified financial advisor for advice tailored to your situation.
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Learn more
Articles to go deeper on the ideas behind this calculator.
Fundamentals
Simple vs. compound interest, explained
Why the same rate can produce very different results over time.
5 min read
Fundamentals
Where simple interest is still used today
Short-term loans, penalty charges, and other everyday examples.
4 min read
Fundamentals
The Rule of 72, explained
A quick mental shortcut for estimating compounding doubling time.
4 min read