To calculate the 50-day moving average, you add up a stock's daily closing price for each of the last 50 trading days (i.e. don't count weekends), and divide by 50: (price 50 days ago + price 49 days ago + price 48 days + . . . + price yesterday + closing price today) divided by 50. To calculate the 200-day moving average, you do the same thing: add up the stock's closing price for each of the last 200 trading days, and divide by 200.
