Thanks guys. Checking it out right now. I'm assuming most people just use this "simple moving average" as opposed to the the exponential?
Simple Moving Average (SMA)
(Click here for a live example of a Simple Moving Average)
A simple moving average is formed by computing the average (mean) price of a security over a specified number of periods. While it is possible to create moving averages from the Open, the High, and the Low data points, most moving averages are created using the closing price. For example: a 5-day simple moving average is calculated by adding the closing prices for the last 5 days and dividing the total by 5.
10+ 11 + 12 + 13 + 14 = 60
(60 / 5) = 12
The calculation is repeated for each price bar on the chart. The averages are then joined to form a smooth curving line - the moving average line. Continuing our example, if the next closing price in the average is 15, then this new period would be added and the oldest day, which is 10, would be dropped. The new 5-day simple moving average would be calculated as follows:
11 + 12 + 13 + 14 +15 = 65
(65 / 5) = 13
Over the last 2 days, the SMA moved from 12 to 13. As new days are added, the old days will be subtracted and the moving average will continue to move over time.
Exponential Moving Average (EMA)
(Click here for a live example of an Exponential Moving Average)
In order to reduce the lag in simple moving averages, technicians often use exponential moving averages (also called exponentially weighted moving averages). EMA's reduce the lag by applying more weight to recent prices relative to older prices. The weighting applied to the most recent price depends on the specified period of the moving average. The shorter the EMA's period, the more weight that will be applied to the most recent price. For example: a 10-period exponential moving average weighs the most recent price 18.18% while a 20-period EMA weighs the most recent price 9.52%. As we'll see, the calculating and EMA is much harder than calculating an SMA. The important thing to remember is that the exponential moving average puts more weight on recent prices. As such, it will react quicker to recent price changes than a simple moving average. Here's the calculation formula.
Exponential Moving Average Calculation
Exponential Moving Averages can be specified in two ways - as a percent-based EMA or as a period-based EMA. A percent-based EMA has a percentage as it's single parameter while a period-based EMA has a parameter that represents the duration of the EMA.
The formula for an exponential moving average is:
EMA(current) = ( (Price(current) - EMA(prev) ) x Multiplier) + EMA(prev)
For a percentage-based EMA, "Multiplier" is equal to the EMA's specified percentage. For a period-based EMA, "Multiplier" is equal to 2 / (1 + N) where N is the specified number of periods.
For example, a 10-period EMA's Multiplier is calculated like this:
(2 / (Time periods + 1) ) = (2 / (10 + 1) ) = 0.1818 (18.18%)
This means that a 10-period EMA is equivalent to an 18.18% EMA.
Note: StockCharts.com only support period-based EMA's.
Below is a table with the results of an exponential moving average calculation for Eastman Kodak. For the first period's exponential moving average, the simple moving average was used as the previous period's exponential moving average (yellow highlight for the 10th period). From period 11 onward, the previous period's EMA was used. The calculation in period 11 breaks down as follows:
(C - P) = (57.15 - 59.439) = -2.289
(C - P) x K = -2.289 x .181818 = -0.4162
( (C - P) x K) + P = -0.4162 + 59.439 = 59.023