Rule of 72 Canada 2025

Rule of 72 Calculator

Enter your interest rate or expected annual return to calculate your doubling time.

Annual Interest Rate or Return (%)

Starting Amount (optional, $)

Common Canadian Rates — How Long to Double?

0.01%

Big Bank Chequing

7,200 years

4.5%

KOHO HISA

~16 years

5.0%

1-Year GIC

~14.4 years

Balanced ETF

~10.3 years

10%

S&P 500 (historical)

~7.2 years

19.99%

Credit Card Debt

~3.6 years (doubles your debt!)

Double Your Savings Faster with KOHO

At 0.01% in a big bank chequing account, your money takes 7,200 years to double. In KOHO's HISA at 4.5%, it doubles in about 16 years — and that's just the savings account, before you invest. Use code 45ET55JSYA for a sign-up bonus.

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What is the Rule of 72?

The Rule of 72 is one of the simplest and most useful shortcuts in personal finance. Divide the number 72 by any annual interest rate, and you get the approximate number of years it takes for an investment to double in value.

Years to Double = 72 ÷ Annual Interest Rate (%)

For example:

At 4%: 72 ÷ 4 = 18 years to double
At 6%: 72 ÷ 6 = 12 years to double
At 8%: 72 ÷ 8 = 9 years to double
At 12%: 72 ÷ 12 = 6 years to double

The rule works in reverse too — to find what interest rate doubles your money in a target number of years, divide 72 by the target years: 72 ÷ 10 years = 7.2% required return.

The Rule of 72 Applied to Canadian Debt

The Rule of 72 is equally powerful for understanding how fast debt grows if unpaid. At 19.99% credit card interest, your balance doubles every 72 ÷ 19.99 = 3.6 years. A $100 credit card balance grows to $20,000 in under 4 years if you only pay the minimum.

This is why high-interest debt always takes priority over investing. The guaranteed return from paying off a 20% credit card beats any investment return available.

Rule of 72 and Canadian Inflation

The same rule applies to how inflation erodes purchasing power. At 3% inflation (close to the Bank of Canada's target), your money's purchasing power halves in 72 ÷ 3 = 24 years. At the peak 2022 inflation of 8.1%, purchasing power halved in about 9 years.

This is why holding large amounts of cash for long periods is financially damaging — inflation silently destroys your purchasing power even as the dollar amount stays the same.

Accuracy of the Rule of 72

The Rule of 72 is an approximation. It's most accurate for rates between 6 and 10%. For lower rates, 69 gives a more precise answer (based on ln(2) = 0.693). For higher rates, 70 is slightly more accurate. But for everyday financial planning, 72 is perfectly useful.

For precise calculations at any rate and with monthly contributions, use the Compound Interest Calculator.