Offering a dollar value when describing a stock's increase in value is meaningless without a reference point. As an example, stating a stock increased by $10 offers no real insight into its growth, because you don't know its starting value. If the stock was originally $500, that $10 increase is no big deal, but if it was originally a dollar stock, then that growth is significant. A better way to describe growth is using percentages, which tells you the amount of growth relative to its initial value.
Subtract the stock's original value from its current value. As an example, if you the stock was originally trading at $50 per share, and three weeks later it traded for $60 per share, you would calculate the difference of $10.
Divide this difference by the original value. Continuing this example, dividing $10 by $50 gives you 0.20.
Multiply by 100 to convert the figure into percentage format. In this example, this gives you a 20 percent increase.