Finance Shortcut

See how fast money doubles at your current return.

The Rule of 72 is a fast estimate for how many years it takes an investment to double. Enter an annual return and compare the shortcut to the exact compounding math, plus rough tripling and quadrupling timelines.

Doubling timeline

The Rule of 72 is the shortcut. The exact result uses annual compounding math for a cleaner comparison.

Rule of 72 estimate 0 years A quick mental-math estimate for doubling time.

Exact doubling time 0 years Calculated with annual compounding.

Difference 0 years How close the shortcut is at this rate.

Rule-of-thumb check Good fit The Rule of 72 tends to work best in the mid-single-digit to low-teen range.

Growth milestones

These bars show rough timelines for common milestones using exact annual compounding at your selected rate.

Double your money 0 years

Triple your money 0 years

Quadruple your money 0 years

At 8.0%, money roughly doubles every 9 years. That means a long horizon matters. A small rate change can shave years off your doubling time.

Compare the shortcuts

Different rules are used for different back-of-the-envelope estimates. This gives you the quick mental-math reference points.

0 years Rule of 69.3 (continuous compounding style estimate)

0 years Rule of 70 (slightly conservative shortcut)

0 years Rule of 72 (popular balance between speed and accuracy)