Step 1: How to use this calculator?

{'step': 1, 'description': 'Apply Rule of 72 formula', 'calculation': '72 ÷ 8 = 9 years'}

Step 2: How to use this calculator?

{'step': 2, 'description': 'Verify with actual compound formula', 'calculation': '(1.08)^9 = 1.999 ≈ 2x'}

Using Rule of 72 for very high interest rates (becomes less accurate)

Not adjusting for inflation when calculating real doubling time

Calculadora Regra 72

Last updated: 2026-08-24

Calculadora Regra 72 — Calcule Years to double = 72 / Interest rate (%). Exemplo: Interest rate 6% annual = Investment doubles in ≈ 12 years. Calculadora gratuita e precisa, sem registo.

Inputs

Result

Enter values and press Calculate

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How to use it

{'step': 1, 'description': 'Apply Rule of 72 formula', 'calculation': '72 ÷ 8 = 9 years'}
{'step': 2, 'description': 'Verify with actual compound formula', 'calculation': '(1.08)^9 = 1.999 ≈ 2x'}

Common mistakes

⚠️ Using Rule of 72 for very high interest rates (becomes less accurate)
⚠️ Not adjusting for inflation when calculating real doubling time
⚠️ Forgetting that the rule assumes compound interest, not simples

Worked example

Estimating how long it takes to double money at 8% annual return using the Rule of 72.

At {tasa_interes}% return, your investment will double in approximately anos_duplicar of {anos_duplicar} years.

Input guide

Field	Typical range
tasa_interes	1-20% annual interest rates