Volatility Drag Calculator

There are two ways to average a string of returns, and they don't agree. The arithmetic mean — add them up, divide — is the number in the brochure. The geometric mean — what your money actually compounds at — is always lower the moment the returns aren't identical, because losses and gains aren't symmetric: a 50% drop needs a 100% climb just to break even, a 20% drop needs 25%. That gap is volatility drag (the 'variance drain'), and it's a direct tax on growth that rises with how bumpy the ride is. This lesson grows the same money two ways — the average compounded smoothly versus the same average lived as a real good-year/bad-year see-saw — and lets you watch the bumpy line peel away below the promise as you crank the volatility, even though the average never moves. It reframes risk: volatility isn't only a wider range of outcomes, it actively lowers the middle of them, which is why diversification and not blowing up matter more than chasing the highest 'average' you can find.

Free and interactive — no sign-up, nothing to install. Read the full lesson for the plain-language explanation.