What is Expected Variance? Variance represents how much a stock moves over a period of time. The statistical calculation for actual variance is the average of the square differences from the mean. Technically, the square of the implied volatility multiplied by the time to expiry (in years) gives us the expected variance up to any given maturity. The variance of one period and another can be added together to calculate the total expected variance of the entire period. Interested in learning more? Related articles What are Vanna Charts?