⏳ 72 ÷ Rate = Years to Double📈 Two Modes🔗 Doubling Chain Visual
Rule of 72 Calculator
The simplest mental math trick in finance. Find how many years to double your money — or what rate you need to double by a target date.
Annual Return Rate
1%40%
Target Doubling Period
1 yr30 yrs
Starting Amount
₹
Years to Double
6 yrs
Your money doubles every 6 years at 12%
Rate Used
12%
Exact Years (ln2)
6.12
Rule of 72 Approx
6.00
Starting Amount
₹0
After 1 Double
₹0
After 2 Doubles
₹0
📝 Rule of 72 Formula
Years = 72 / 12% = 6.00 years | Exact = ln(2) / ln(1.12) = 6.12 years
Rule of 72: Years = 72 ÷ Annual Rate% | Reverse: Rate = 72 ÷ Target Years Exact Formula: t = ln(2) / ln(1 + r) = 0.693 / r | Accurate for rates 6%–20%
🔗 Doubling Chain — How your money grows
📅 Doubling Time at Common Rates
Investment Type
Rate
Rule of 72
Exact Years
Growth Curve — Doublings Visualized
ⓘ Rule of 72 is an approximation. Error is <1% for rates 6–18%. For continuous compounding use 69.3. Always verify with exact logarithm formula for critical financial decisions.
Frequently Asked Questions
What is the Rule of 72? +
The Rule of 72 is a mental math shortcut: Years to double = 72 ÷ Annual Return %. At 12%, money doubles in 72/12 = 6 years. It applies to any compounding growth — investments, inflation, GDP, population. Accurate within 1% for rates 6-18%.
How long to double money in FD in India? +
At current FD rates: 6.5% → 72/6.5 = 11.1 years. 7% → 10.3 years. 7.5% → 9.6 years. PPF at 7.1% → 10.1 years. Equity at 12% CAGR → 6 years. Equity at 15% → 4.8 years. This is why long-term equity investing creates dramatically more wealth than FDs.
What rate do I need to double money in 5 years? +
Rate Required = 72 ÷ Target Years. To double in 5 years: 72/5 = 14.4% p.a. In 7 years: 10.3% p.a. In 10 years: 7.2% p.a. In 3 years: 24% p.a. Mid-cap and small-cap equity funds can achieve 14-18% over 10+ years, but carry higher volatility.
Can I apply Rule of 72 to inflation? +
Yes. At 6% inflation: prices double in 72/6 = 12 years. ₹1 lakh worth of goods costs ₹2 lakh in 12 years. At 8% food inflation: prices double in just 9 years. This is why you must invest to beat inflation — FD at 7% barely keeps pace, while equity at 12%+ grows real wealth.
How accurate is the Rule of 72? +
Very accurate for 6-18% rates. At 8%: Rule of 72 gives 9 years, exact = 9.01 years (error: 0.1%). At 12%: gives 6 years, exact = 6.12 years (error: 2%). At 20%: gives 3.6 years, exact = 3.80 years (error: 5.3%). For rates above 20%, use exact formula t = ln(2)/ln(1+r).
What is Rule of 69.3 vs Rule of 70 vs Rule of 72? +
69.3 is mathematically exact (ln(2) × 100). Rule of 70 is used in economics. Rule of 72 is preferred in finance because 72 is divisible by 2, 3, 4, 6, 8, 9, 12 — making mental math easier. For practical investing: use Rule of 72.