Free Online Tool

Compound Interest Calculator

Visualize how your money grows over time — with compound interest, regular contributions, inflation adjustment, and interactive charts.

Compound interest Monthly contributions Multiple frequencies 100% free
Investment Parameters
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Principal amount
%
yrs
₹
Advanced Options
Enter your investment details and click Calculate Growth
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Compound Interest Formulas Explained

① Basic Compound Interest

A = P × (1 + r/n)n×t

  • A — Final amount
  • P — Principal
  • r — Annual rate (decimal)
  • n — Compounding periods/year
  • t — Time in years

② Future Value with Contributions

FV = PMT × [((1 + r/n)n×t − 1) ÷ (r/n)]

  • FV — Future value of contributions
  • PMT — Payment per period
  • r — Annual rate (decimal)
  • n — Compounding periods/year
  • t — Time in years

③ Real Return — Fisher Equation

rreal = (1 + rnom) ÷ (1 + i) − 1

  • rreal — Inflation-adjusted return
  • rnom — Nominal interest rate
  • i — Annual inflation rate

⚡ The Rule of 72

Years to double ≈ 72 ÷ Interest Rate

  • At 6% → doubles in 12 years
  • At 8% → doubles in 9 years
  • At 10% → doubles in 7.2 years
  • At 12% → doubles in 6 years

How to Use the Calculator

1

Enter Principal

Type your initial investment amount.

2

Set Rate & Duration

Use sliders for return rate and investment period.

3

Add Contributions & Calculate

Set regular contributions, click Calculate Growth.

💡 Pro Tip: Start as early as possible. ₹5,000 invested at age 25 at 8% grows to ~₹1,59,600 by age 65. Waiting until 35 yields only ~₹73,900 — less than half.

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Frequently Asked Questions

Compound interest is interest calculated on both the initial principal and all accumulated interest from previous periods. Unlike simple interest, compound interest grows exponentially — you earn interest on your interest.

More frequent compounding yields higher returns. On ₹10,000 at 7% over 10 years: annually → ₹19,672, monthly → ₹20,097, daily → ₹20,137. The gap grows with larger amounts and longer time horizons.

The Rule of 72 estimates how many years it takes for your investment to double. Divide 72 by your annual interest rate: at 8%, it doubles in ~9 years. The calculator shows this automatically.

Using the Fisher equation, the calculator adjusts your nominal return for inflation. A 7% return with 3% inflation gives a real return of ~3.88%. This shows what your future balance is worth in today's purchasing power.

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Privacy & security notice

This compound interest calculator runs entirely in your web browser. No data is ever transmitted, stored, or logged by our servers. All calculations are instant and completely private.