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Finance Calculators

Rule of 70 Calculator

Verified formula Updated Jun 2026 Private — runs on your device

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Verified formula Private

Time to double

10.00

For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.

How to use the Rule of 70 Calculator

The Rule of 70 Calculator works out your time to double in an instant. Enter growth rate per period and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.

  1. Enter the growth rate per period.
  2. Read off your time to double — the calculator updates automatically, with no button to press.

Formula

The Rule of 70 Calculator uses the formula:

Time to double = 70 ÷ Growth rate per period

Worked example

For example, with growth rate per period of 7%, the time to double is 10.00.

Inputs used
Growth rate per period 7%
Results
Time to double 10.00

Results are estimates for educational use, not professional advice.

Frequently asked questions

A shortcut for doubling time: divide 70 by the growth rate. At 7% growth, a value doubles in about 10 years.

Both estimate doubling time. The rule of 70 is often used for population and inflation; the rule of 72 is common in finance.

It is an approximation. It is most accurate for moderate growth rates and slightly off at very high rates.

Estimating how fast investments, populations or prices double, without a calculator or logarithms.

The Rule of 70 Calculator uses the formula: Time to double = 70 ÷ Growth rate per period. For example, with growth rate per period of 7%, the time to double is 10.00.

Enter the growth rate per period. Read off your time to double — the calculator updates automatically, with no button to press.

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