Rule of 72 / 114 / 144 Calculator

Use the Rule of 72, 114, and 144 to instantly calculate how fast compound growth will double, triple, or 4× your investment.

Expected annual return or interest rate (e.g. 8% for FD/Debt, 12% for Equity).

How it works

The Rule of 72 is derived from the natural logarithm of 2 (ln(2) ≈ 0.693, approximated to 72 for divisibility). Similarly, ln(3) ≈ 1.0986 (Rule of 114 to triple) and ln(4) ≈ 1.386 (Rule of 144 to quadruple).

Formula

T_2× ≈ (72 / r), T_3× ≈ (114 / r), T_4× ≈ (144 / r)

A mental math shortcut based on compound logarithms: divide 72 by your annual return rate to approximate doubling time.

SymbolVariableUnitDescription
T_2×Years to double investmentyears
T_3×Years to triple investmentyears
T_4×Years to quadruple investmentyears
rAnnual return / interest rate percentage%

Worked example

Investment earning 8% per annum

Annual Rate:
8%

Years to double = 72 / 8 = 9.0 years. Years to triple = 114 / 8 = 14.25 years. Years to 4× = 144 / 8 = 18.0 years. (At 12% equity returns, money doubles in just 72 / 12 = 6.0 years!).

Limitations

Approximation is designed for steady annual compounding without market volatility.

Frequently asked questions

How accurate is the Rule of 72?

The Rule of 72 is remarkably accurate for interest rates between 6% and 10%. For extremely high rates (>20%), the exact logarithmic formula ln(2)/ln(1+r) yields a slightly more precise duration.

Can I use the Rule of 72 for inflation?

Yes! Divide 72 by the annual inflation rate to find how many years it will take for the cost of living to double. At 6% inflation, prices double every 72 / 6 = 12 years.

What is the Rule of 114 and Rule of 144?

Rule of 114 calculates the years needed to triple (3×) your money (114 / Rate). Rule of 144 calculates the years needed to quadruple (4×) your capital (144 / Rate).

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Last reviewed: 2026-08-22.