Power Calculators

💵 Simple Interest Calculator (SI = PRT/100)

SI = P × R × T ÷ 100 — the school formula, done for you.

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Formula at a glance

Simple Interest Calculator: Simple interest — SI = P × R × T / 100. Example: ₹50,000 at 6% for 3 years → Simple interest: ₹9,000.00
How the Simple Interest Calculator works: Simple interest — SI = P × R × T / 100

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📘 About the Simple Interest Calculator

Simple interest is charged or earned only on the original principal, not on interest already added. It is used for short-term loans, some personal and gold loans, car loans quoted on a flat rate, and in school maths. The interest is the same every year.

Enter the principal, the yearly rate and the time (in years, months or days). The calculator gives the simple interest, the total amount, the interest per year and month, and what compound interest would have given, with a year-by-year comparison.

🧮 Formula

Simple interest
SI = P × R × T / 100
Amount
A = P + SI
Rearranged
P = 100·SI/(RT), R = 100·SI/(PT), T = 100·SI/(PR)

✏️ Worked examples

₹50,000 at 6% for 3 years

You enter
Currency₹ Indian rupee
Principal P50000
Rate R6 % a year
Time T3
Time inYears
You get
Simple interest₹9,000.00
Total amount (P + SI)₹59,000.00
Interest per year · per month₹3,000.00 · ₹250.00
Time in years3
Compound interest (yearly) instead₹9,550.80 (₹550.80 more)

₹9,000.00.

₹2 lakh at 9% for 18 months

You enter
Currency₹ Indian rupee
Principal P200000
Rate R9 % a year
Time T18
Time inMonths
You get
Simple interest₹27,000.00
Total amount (P + SI)₹2,27,000.00
Interest per year · per month₹18,000.00 · ₹1,500.00
Time in years1.5
Compound interest (yearly) instead₹27,598.68 (₹598.68 more)

₹27,000.00.

🧭 How to use this calculator

What you enter

  • Currency
  • Principal P
  • Rate R (% a year)
  • Time T
  • Time in

What you get

  • Simple interest
  • Total amount (P + SI)
  • Interest per year · per month
  • Time in years
  • Compound interest (yearly) instead

❓ Frequently asked questions

What is the difference between simple and compound interest?

Simple interest is on the principal only; compound interest is also on the interest already earned, so it grows faster.

How do I calculate simple interest for months?

Divide the months by 12 to get years: 18 months = 1.5 years.

What is a flat interest rate?

Interest worked out on the full loan for the whole term (simple interest), even though you repay it gradually — so the real rate is higher.

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