Sharpe ratio
A measure of return earned per unit of risk (volatility) — a way to compare strategies on reward relative to the bumpiness of the ride.
The Sharpe ratio divides a strategy's return, above the yield on cash, by its volatility. It answers a fairer question than raw return alone: how much reward did an investor earn for each unit of risk taken along the way?
A higher Sharpe means steadier returns for a given result, or a stronger result for the same swings. Like any single number it can mislead — it treats upside and downside volatility alike — so it is read next to drawdown and other measures, never on its own.