What is the rule of 72 in consulting?

What Is the Rule of 72 and Why Consultants Love It?

Chances are, if you've sat in a strategy meeting or flipped through a growth presentation, you've heard someone casually drop the "Rule of 72." It’s not corporate jargon—it’s a simple, powerful mental model borrowed from finance and widely used in consulting for quick, back-of-the-envelope projections.

The rule is straightforward: Divide 72 by your expected annual rate of return, and you’ll get a rough estimate of how many years it will take for an investment to double. For example, at a 6% annual return, your money doubles in about 12 years (72 ÷ 6 = 12). At 8%, it takes just 9 years.

Why do consultants lean on it so much? Because in high-stakes boardrooms, clarity wins. Instead of diving into complex financial models during early discussions, consultants use this rule to make growth tangible. When a client asks, “What if we grow revenue at 10% a year?” the consultant can instantly reply, “Your business would double in roughly 7.2 years,” thanks to 72 ÷ 10.

It’s not perfectly precise—especially at extreme interest rates—but it’s shockingly accurate for typical returns and far easier to calculate on the fly than compound interest formulas. Plus, it works beyond money: some adapt it to estimate doubling times for users, market share, or operational scale.

While it doesn’t replace detailed financial analysis, the Rule of 72 thrives in the space between insight and simplicity. In a world overflowing with data, sometimes the best tool is the one you can remember without a spreadsheet.