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Finance

Rule of 72

A quick math trick that estimates how many years it takes for money to double at a certain interest rate.

The Rule of 72 works best for rates between 1% and 20%. It's not perfect math but it's close enough for quick decisions about investing or debt.

It's like a cheat code for money — divide 72 by the interest rate and you instantly know when your cash will double.

Real world: At 8% interest, money doubles in about 9 years (72 ÷ 8 = 9). At 3%, it takes 24 years.

💡 Memorize the Rule of 72 — it's the fastest way to see why 8% investing beats 3% savings every single time.