Simple & Compound Interest

Compare simple and compound interest side by side — year-by-year table, growth chart, full substitution steps, the Class 10 CI − SI shortcut and a reverse calculator for P, R or T.

Class 7–10 Mathematics Growth chart Yearly table

Simple interest is SI = P × R × T ÷ 100, so ₹10,000 at 8% for 5 years earns ₹4,000. Compound interest uses A = P(1 + R ÷ 100)^T; the same deposit grows to ₹14,693.28, making the interest ₹4,693.28. CI is larger because each year's interest also earns interest, while SI is only ever paid on the original principal.

Your deposit or loan

Type the values from your question or bank slip.

Currency
₹
% per year
Time (T)
years
months
Try an example
Simple interest
Compound interest
CI − SI

Growth over time

Hover or tap the chart to read the amount at any point.

Amount with SIAmount with CIPrincipal

Year-by-year table

Opening balance, interest earned and closing balance for both methods.

YearSimple interestCompound interest
OpeningInterestClosingOpeningInterestClosing

Step-by-step substitution

Simple interest

    Compound interest

      Class 10 shortcut: CI − SI

      For interest compounded annually, the difference between CI and SI on the same P and R has a quick formula.

      How it works

      Why compound interest grows faster

      Simple interest is paid only on the money you started with. Compound interest is also paid on the interest already added — “interest on interest”.

      Enter P, R and T

      Time can be in years and months, e.g. 2 years 6 months.

      Pick how often CI is added

      Annually, half-yearly, quarterly (most bank FDs) or monthly.

      Compare

      Read SI, CI and the gap between them, then follow the chart and yearly table.

      Go in reverse

      Use Reverse SI when the question gives the interest and asks for P, R or T.

      Simple interest

      SI = P × R × T ÷ 100

      Amount A = P + SI. The interest is the same every year, so the amount grows in a straight line.

      Compound interest

      A = P (1 + R ÷ 100n)nT

      n = times per year (1, 2, 4 or 12). CI = A − P. Half-yearly: halve the rate and double the time.

      CI − SI shortcuts

      Annual compounding, same P and R:

      2 years: P (R/100)²
      3 years: P (R/100)² (3 + R/100)

      Reverse formulas

      P = 100 × SI ÷ (R × T) · R = 100 × SI ÷ (P × T) · T = 100 × SI ÷ (P × R)

      Money doubles under SI when R × T = 100, e.g. 10% for 10 years.

      Part years: when the time is not a whole number of compounding periods (for example 2 years 6 months compounded annually), this tool follows the usual textbook and bank method — compound interest for the full periods, then simple interest on that amount for the remaining part.
      Questions & answers

      Simple & Compound Interest — your questions

      What is the formula for simple interest?

      SI = P × R × T ÷ 100, where P is the principal, R is the rate per year and T is the time in years. The amount is A = P + SI. For ₹5,000 at 6% for 3 years the interest is 5000 × 6 × 3 ÷ 100 = ₹900, so the amount is ₹5,900. The interest is the same every year, so the amount grows in a straight line.

      What is the difference between simple and compound interest?

      Simple interest is paid only on the money you started with, so it is the same every year. Compound interest is paid on the principal plus the interest already added, so it grows faster each year. On ₹10,000 at 8% for 5 years, SI gives ₹4,000 while annual CI gives ₹4,693.28 — a gap of ₹693.28.

      What is the CI minus SI shortcut for Class 10?

      When interest is compounded annually on the same principal and rate, the difference for 2 years is P(R/100)², and for 3 years it is P(R/100)²(3 + R/100). For ₹8,000 at 5% over 2 years that is 8000 × 0.05² = ₹20. It is a fast way to check an answer or solve for P when only the difference is given.

      How do I calculate compound interest half-yearly or quarterly?

      Use A = P(1 + R ÷ 100n)^(nT), where n is the number of times interest is added per year. For half-yearly compounding halve the rate and double the time, and for quarterly divide the rate by 4 and multiply the time by 4. The more often interest is added, the larger the final amount for the same yearly rate.

      How do I find the principal, rate or time from the interest?

      Rearrange the simple interest formula: P = 100 × SI ÷ (R × T), R = 100 × SI ÷ (P × T) and T = 100 × SI ÷ (P × R). If ₹5,000 earns ₹1,800 at 6% per year, then T = 100 × 1800 ÷ (5000 × 6) = 6 years. If the question gives the amount, subtract the principal first to get SI.

      In how many years does money double at simple interest?

      Money doubles under simple interest when R × T = 100, because the interest then equals the principal. So 10% per year takes 10 years, 8% takes 12.5 years and 5% takes 20 years. Compound interest is much faster — at 8% compounded annually money doubles in a little over 9 years rather than 12.5.