How is yahoo finance P/E Ratio TTM calculated?
The correct p/e for bp.l is 5.80. Bp.l is on the London stock exchange and prices are in local currency. The share price of 493 is reported in pence (not dollars). The EPS is reported in pounds. Using .85 pounds = 85 pence, you calculate the EPS as follows: 493.40/85 = 5.80 PE Yahoo totally screwed up. They converted the .85 pounds into US dollars ($1.34) but didn't convert the 493 pence. By using the 493 as dollars, they got 493.9/1.34 = 368 pe! Notice that Yahoo reports the American Depository Shares (symbol 'BP') with an EPS of $8.06. That correctly reflects that there are 6 shares of BP.l per ADS (1.34 * 6 = 8.04). But why is the share price listed at $46.69? Well...  493 GBp (pence) = 4.93 pounds 4.93 pounds  = 7.73 USD 7.73 USD * 6 shares per ADS = 46.38 USD "P/E is Price divided by Earnings Per Share (EPS). P/E TTM is Price divided by the actual EPS earned over the previous 12 months - hence ""Trailing Twelve Month"". In Forward P/E is the ""E"" is the average of analyst expectations for the next year in EPS. Now, as to what's being displayed. Yahoo shows EPS to be 1.34. 493.90/1.34 = P/E of 368.58 Google shows EPS to be 0.85. 493.40/0.85 = P/E of 580.47 (Prices as displayed, respectively) So, by the info that they are themselves displaying, it's Google, not Yahoo, that's displaying the wrong P/E. Note that the P/E it is showing is 5.80 -- a decimal misplacement from 580 Note that CNBC shows the Earnings as 0.85 as well, and correctly show the P/E as 580 http://data.cnbc.com/quotes/BP.L A quick use of a currency calculator reveals a possible reason why EPS is listed differently at yahoo. 0.85 pounds is 1.3318 dollars, currently. So, I think the Yahoo EPS listing is in dollars. A look at the last 4 quarters on CNBC makes that seem reasonable: http://data.cnbc.com/quotes/BP.L/tab/5 those add up to $1.40."
I said Yahoo because it was hot for a while and now it's not. Tons of people who bought at the top when their P/E was stupid, lost their ass. That was entirely the point. Websites, like Hot Pockets, may exist forever but they don't stay hot forever. Standard Deviation is a mathematical term that is useful in many areas. It can be considered a measure of how tight the data points are to the average. If there is consistency in the measurement system, then a point that is two standard from the average can be considered an outlier. It doesn't even need to be time based. We can say that a child born weighing less than X pounds is more than 2 standard deviations below the average.  Using it to look at a price or an index value doesn't make a lot of sense because many expect there to be long term growth. For example you would never say that you will buy a new jacket for your child when they are two standard deviations above their average height. You can say you will buy or sell a financial instrument when the P/E ratio is 2 standard deviations from some average. It could be the average of the long term history, or the index, or the sector. You could do the same thing for earnings per share or many other business of financial statistics. A standard deviation calculated from a time series assumes that the measurement will normally stay withing some bounds. And that straying from those bounds is a sign of the right time to buy or sell. Options - yes we can :) Options tickers on Yahoo! Finance will be displayed as per new options   symbology announced by OCC. The basic parts of new option symbol are: Root symbol + Expiration   Year(yy)+ Expiration Month(mm)+ Expiration Day(dd) + Call/Put   Indicator (C or P) + Strike price Ex.: AAPL January 19 2013, Put 615 would be AAPL130119P00615000 http://finance.yahoo.com/q?s=AAPL130119P00615000&ql=1 Futures - yes as well (: Ex.: 6A.M12.E would be 6AM12.CME using Yahoo Finance symbology. (simple as that, try it out) Get your major futures symbols from here: http://quotes.ino.com/exchanges/exchange.html?e=CME what do you mean exactly?  Do you have a future target price and projected future dividend payments and you want the present value (time discounted price) of those? Edit: The DCF formula is difficult to use for stocks because the future price is unknown.  It is more applicable to fixed-income instruments like coupon bonds.  You could use it but you need to predict / speculate a future price for the stock. You are better off using the standard stock analysis stuff: Learn Stock Basics - How To Read A Stock Table/Quote The P/E ratio and the Dividend yield are the two most important.  The good P/E ratio for a mature company would be around 20.  For smaller and growing companies, a higher P/E ratio is acceptable.  The dividend yield is important because it tells you how much your shares grow even if the stock price stays unchanged for the year. HTH PEG is Price/Earnings to Growth.  It is calculated as Price/Earnings/Annual EPS Growth.  It represents how good a stock is to buy, factoring in growth of earnings, which P/E does not.  Obviously when PEG is lower, a stock is more undervalued, which means that it is a better buy, and more likely to go up. Additional References: Google Finance gives you this information. Profit after tax can have multiple interpretations, but a common one is the EPS (Earnings Per Share).  This is frequently reported as a TTM number (Trailing Twelve Months), or in the UK as a fiscal year number.  Coincidentally, it is relatively easy to find the total amount of dividends paid out in that same time frame. That means calculating div cover is as simple as:  EPS divided by total dividend.  (EPS / Div). It's relatively easy to build a Google Docs spreadsheet that pulls both values from the cloud using the GOOGLEFINANCE() function.  I suspect the same is true of most spreadsheet apps.  With a proper setup, you can just fill down along a column of tickers to get the div cover for a number of companies at once. "Using your example link, I found the corresponding chart for a stock that trades on London Stock Exchange: https://ca.finance.yahoo.com/echarts?s=RIO.L#symbol=RIO.L;range=1d As you can see there, the chart runs from ~8:00am to ~4:30pm, and as I write this post it is only 2:14pm Eastern Time.  So clearly this foreign chart is using a foreign time zone.  And as you can see from this Wikipedia page, those hours are exactly the London Stock Exchange's hours. Additionally, the closing price listed above the graph has a timestamp of ""11:35AM EST"", meaning that the rightmost timestamp in the graph (~4:30pm) is equal to 11:35AM EST.  16:30 - 11:30 = 5 hours = difference between London and New York at this time of year. So those are two data points showing that Yahoo uses the exchange's native time zone when displaying these charts."