Rule of 72 Calculator — How Long to Double Your Money?

Use this calculator to quickly estimate how long it will take for your money to double at a given interest rate.

Calculate Your Investment Growth

Interest rate %:

What is the Rule of 72?

The Rule of 72 is a simple formula used in finance to estimate the number of years required to double an investment at a given annual interest rate. It provides a quick way to evaluate potential returns on investments.

How to Calculate Investment Growth?

The formula for the Rule of 72 is:

Years to Double = 72 ÷ Interest Rate

For example, if you invest money at an annual return of 8%, your investment will approximately double in:

72 ÷ 8 = 9 years

Why is the Rule of 72 Useful?

• Quickly estimate investment growth without complex calculations.
• Compare different investment options (stocks, bonds, real estate, savings).
• Plan financial goals (retirement, savings, wealth accumulation).

Limitations of the Rule of 72

While the Rule of 72 is useful, it assumes constant interest rates and ignores market fluctuations. It works best for rates between 6% and 10%, while for higher or lower rates, slight adjustments are necessary.

Real-Life Examples

• If the stock market grows at 8% per year, investments will double in 9 years.
• If inflation averages 3% per year, prices double in 24 years.
• A bank savings account at 1% interest will take 72 years to double!

Frequently Asked Questions (FAQ)

Can the Rule of 72 be used for inflation?

Yes! If inflation is 4% per year, the purchasing power of money will halve in 18 years (72 ÷ 4 = 18).

Does the Rule of 72 work for all interest rates?

It works best for interest rates between 6% and 10%. For very high or low rates, other formulas like the Rule of 69 or 70 are more accurate.

Want to see how much to save? Use our Savings Goal Calculator to plan your investments and reach your financial targets faster.

How can I use this rule for retirement planning?

If your investments yield 8% annually, your retirement savings will double every 9 years. This helps plan how much you need to save today.

Conclusion

The Rule of 72 is a powerful tool for quickly estimating investment growth. Whether planning for retirement, comparing savings options, or tracking inflation, this simple formula helps make better financial decisions.

Try our Rule of 72 Calculator now and see how fast your money can grow!