Compound interest calculator — the 8th wonder of the world.
Compounding is the single most powerful idea in personal finance — every year's interest earns its own interest the year after. We show the maturity value, the simple-interest comparison, and the exact "compounding bonus" — the extra money you make just by keeping returns in the system.
Your inputs
The compounding bonus
Simple interest on the same inputs gives ₹2.00 L. Compounding takes you to ₹2.59 L — an extra ₹59,374. That's a 59% boost over simple interest, earned purely by keeping returns in the system.
The compounding bonus scales non-linearly with tenure — at 10 years it's ~60% of simple interest (at 10% rate), at 20 years it's over 3×, at 30 years it's 10×. This is why long-horizon SIPs make sense and short-term trading rarely does.
Rule of 72 — doubling time shortcut
At 10% annual return, your money doubles in roughly 7.2 years. Works best for rates between 4% and 15%. At 12% (equity long-term average), money doubles every 6 years.
The formula
M = P × (1 + r/f)^(f·t) M = maturity amount P = principal r = annual rate (decimal, e.g. 10% → 0.10) f = compoundings per year (annual=1, half-yearly=2, quarterly=4, monthly=12) t = years
More frequent compounding = slightly higher return. Quarterly vs annual on a 10-year 10% investment adds about 3.5%. Monthly vs annual adds ~4.5%. Beyond quarterly the incremental gain is small.
Rule of 72 — your mental shortcut
Divide 72 by the annual return to get approximate doubling years. Works well for rates between 4% and 15%:
- • At 6% (FD / PPF rough) → 12 years to double
- • At 8% (corporate debt) → 9 years
- • At 10% (balanced fund) → 7.2 years
- • At 12% (equity long-term) → 6 years
- • At 15% (small-cap bull) → 4.8 years
- • At 20% (rare, unsustainable) → 3.6 years
Rule of 72 is derived from ln(2) ≈ 0.693 and is accurate within 2-3% for typical return ranges. For rates above 20%, use 70 instead of 72 for closer approximation.
Put compounding to work
Research tool · not investment advice.
Axel Markets is an information + analytics product. We are not a SEBI-registered Research Analyst (RA) or Investment Adviser (IA). Nothing on this page is a buy, sell, or hold recommendation. Past performance is not indicative of future returns. Verify all data against the authoritative source (NSE, BSE, AMFI, SEBI, company RHP / factsheet) before acting. Return rates used here are nominal (not inflation-adjusted). For goal planning, subtract expected inflation (~6% India long-term) from the nominal rate to get real return.