Time to Double Money Calculator

## What is the Time to Double Money Calculator? The Time to Double Money Calculator uses the exact compound interest formula to tell you precisely how many years your investment takes to double. While the popular Rule of 72 gives a quick approximation (72 / rate = years to double), the exact formula gives a more accurate answer. ## Formula Used Exact Formula: Years to Double = log(2) / log(1 + r) Where r = annual rate of return Rule of 72 (approximation): Years to Double approximately 72 / Rate (%) Comparison at 12% return: - Rule of 72: 72/12 = 6 years - Exact formula: log(2) / log(1.12) = 6.12 years ## Worked Example Investment: Rs 1,00,000, Return: 12% p.a. Years to double = log(2) / log(1.12) = 6.12 years Rule of 72 estimate: 72 / 12 = 6.00 years After 6.12 years, your Rs 1 lakh becomes Rs 2 lakh. After 12.24 years, it becomes Rs 4 lakh. After 18.36 years, it becomes Rs 8 lakh. ## Frequently Asked Questions 1. What is the Rule of 72? The Rule of 72 is a quick mental math trick to estimate how many years an investment takes to double: divide 72 by the annual return rate. At 12% return: 72 / 12 = 6 years. 2. How long does it take to double money in different investments in India? At 7% (PPF, senior citizen FD): approximately 10.3 years At 8% (bank FD): approximately 9 years At 10% (balanced debt fund): approximately 7.2 years At 12% (equity mutual fund): approximately 6.1 years At 15% (growth stocks): approximately 5 years 3. Does doubling time consider inflation? No, the doubling time calculation uses nominal returns. A PPF investment at 7.1% nominally doubles in approximately 10 years, but in real terms (after 5% inflation), it takes approximately 14 years to maintain the same purchasing power. 4. What rate of return should I use for doubling calculation? Use a conservative rate for planning: PPF: 7.1%, Bank FD: 6 to 7%, Debt fund: 7 to 8%, Balanced fund: 10%, Equity mutual fund: 12%, Direct equity (experienced investor): 15%. 5. Is the Rule of 69 more accurate than Rule of 72? The Rule of 69 (or 70) is slightly more accurate for continuous compounding or daily compounding. For annual compounding (most investments), Rule of 72 is sufficiently accurate.