Week 2: The Rule of 72 – How to Double Your Money

What if I told you there’s a simple formula that can estimate how long it takes for your money to double? No complicated math, no spreadsheets—just one number: 72.

What is the Rule of 72?

The Rule of 72 is a quick way to estimate how long an investment will take to double, based on its interest rate. The formula is:

72 ÷ Interest Rate = Years to Double

Let’s break it down:

• At 8% interest, your money doubles in 9 years (72 ÷ 8 = 9).

• At 12% interest, it takes 6 years (72 ÷ 12 = 6).

• At 2% interest, it takes 36 years (72 ÷ 2 = 36).

This is why investing in a savings account earning 0.5% interest won’t build wealth!

Why This Matters for You

If you’re keeping money in a low-interest savings account instead of investing, you’re losing money every year to inflation. Let’s say you put $10,000 in an account earning 1% interest. In 72 years, it will double to $20,000—but inflation will make that money worth much less.

Now, take that same $10,000 and invest it at 8%—it doubles every 9 years, turning into nearly $160,000 in 36 years. That’s the power of investing.

How to Make the Rule of 72 Work for You

• Start investing today, even if it’s small. Time in the market beats timing the market.

• Look for investments with solid returns. Index funds, stocks, real estate—each has different growth potential.

• Avoid high-interest debt. Just like money grows with compound interest, so does debt.

Are you currently investing? If not, what’s stopping you? Let’s talk in the comments!