How do you calculate the P/E ratio by industry?
You could sum the P/E ratio of all the companies in the industry and divide it by the number of companies to find the average P/E ratio of the industry.  Average P/E ratio of industry  = Sum of P/E ratio of all companies in   Industry / Number of companies in industry
"Calculating beta is finding the correlation between the dependent variable, MSCI world benchmark, and the independent variable, your companies. If you know how to run liner regression models, run each company as the independent variable with the dependent MSCI. You can use Excel to gather this result (Y = MSCI price change at closing hour while X = company stock price closing prince). Running the regression will give you the Beta (and alpha when doing portfolios); which (from linear algebra) is the ""m"" in y = mx + b" "If you look at the biotech breakdown, you'll find a lot of NAs when it comes to P/E since there are many young biotech companies that have yet to make a profit.  Thus, there may be something to be said for how is the entire industry stat computed. Biotechnology can include pharmaceutical companies that can have big profits due to patents on drugs. As an example, look at Shire PLC which has a P/E of 1243 which is pretty high with a Market Capitalization of over a billion dollars, so this isn't a small company.  I wonder what dot-com companies would have looked like in 1998/1999 that could well be similar as some industries will have bubbles you do realize, right? The reason for pointing out the Market Capitalization is that this a way to measure the size of a company, as this is merely the sum of all the stock of the company.  There could be small companies that have low market capitalizations that could have high P/Es as they are relatively young and could be believed to have enough hype that there is a great deal of confidence in the stock.  For example, Amazon.com was public for years before turning a profit.  In being without profits, there is no P/E and thus it is worth understanding the limitations of a P/E as the computation just takes the previous year's earnings for a company divided by the current stock price.  If the expected growth rate is high enough this can be a way to justify a high P/E for a stock.  The question you asked about an industry having this is the derivation from a set of stocks.  If most of the stocks are high enough, then whatever mean or median one wants to use as the ""industry average"" will come from that." To calculate you take the Price and divide it by the Earnings, or by the Sales, or by the Free Cash Flow. Most of these calculations are done for you on a lot of finance sites if the data is available. Such sites as Yahoo Finance and Google Finance as well as my personal favorite: Morningstar So, the price-earnings ratio is price over earnings, easy enough. But obviously earnings are not static. In the case of a growing company, the earnings will be higher in the future. There will be extra earnings, above and beyond what the stock has right now. You should consider the future earnings in your estimate of what the company is worth now. One snag: Those extra earnings are future money. Future-money is an interesting thing, it's actually worth less than present-money- because of things like inflation, but also opportunity cost.  So if you bought $100 in money that you'll have 20 years from now, you'd expect to pay less than $100. (The US government can sell you that money. It's called a Series EE Savings Bond and it would cost you $50. I think. Don't quote me on that, though, ask the Treasury.) So you can't compare future money with present-money directly, and you can't just add those dollars to the earnings . You need to compute a discount. That's what discounted cash-flow analysis is about: figuring out the future cash flow, and then discounting the future figuring out what it's worth now. The actual way you use the discount rate in your formula is a little scarier than simple division, though, because it involves discounting each year's earnings (in this case, someone has asserted a discount of 11% a year, and five years of earnings growth of 10%). Wikipedia gives us the formula for the value of the future cash flow:  essentially adding all the future cash flows together, and then discounting them by a (compounded) rate. Please forgive me for not filling this formula out; I'm here for theory, not math. :) Your analysis is correct.  The income statement from Google states that LinkedIn made $3.4 million in 2010 - the same number you backed into by using the P/E ratio.  As you point out, the company seems overvalued compared to other mature companies.  There are companies, however, that posts losses and still trade on exchanges for years.  How should these companies be valued?  As other posters have pointed out there are many different ways to value a company.  Some investors may be speculating on substantial growth.  Others may be speculating on IPO hype. Amazon did not make a profit until 2003.  Its stock had been around for years before that and even split many times.  If you bought the stock in 1998 and still have it you would be doing quite well. Having all of the numbers you posted is a start. It's what you need to perform the calculation.  The final word, however, comes from the company itself, who are required to issue a determination on how the spin-off is valued. Say a company is split into two. Instead of some number of shares of each new company, imagine for this example it's one for one. i.e. One share of company A becomes a share each in company B and company C. This tell us nothing about relative valuation, right? Was B worth 1/2 of the original company A, or some other fraction? Say it is exactly a 50/50 split. Company A releases a statement that B and C each should have 1/2 the cost basis of your original A shares. Now, B and C may very well trade ahead of the stock splitting, as 'when issued' shares. At no point in time will B and C necessarily trade at exactly the same price, and the day that B and C are officially trading, with no more A shares, they may have already diverged in price. That is, there's nothing you can pull from the trading data to identify that the basis should have been assigned as 50% to each new share. This is my very long-winded was of explaining that the company must issue a notice through your broker, and on their investor section of their web site, to spell out the way you should assign your basis to each new stock. "You could not have two stocks both at $40, both with P/E 2, but one an EPS of $5 and the other $10.  EPS = Earnings Per Share P/E = Price per share/Earnings Per Share So, in your example, the stock with EPS of $5 has a P/E of 8, and the stock with an EPS of $10 has a P/E of 4.  So no, it's not valid way of looking at things, because your understanding of EPS and P/E is incorrect. Update: Ok, with that fixed, I think I understand your question better. This isn't a valid way of looking at P/E. You nailed one problem yourself at the end of the post: The tricky part is that you have to assume certain values remain   constant, I suppose But besides that, it still doesn't work. It seems to make sense in the context of investor psychology: if a stock is ""supposed to"" trade at a low P/E, like a utility, that it would stay at that low P/E, and thus a $1 worth of EPS increase would result in lower $$ price increase than a stock that was ""supposed to"" have a high P/E. And that would be true. But let's game it out: Scenario Say you have two stocks, ABC and XYZ. Both have $5 EPS. ABC is a utility, so it has a low P/E of 5, and thus trades at $25/share. XYZ is a high flying tech company, so it has a P/E of 10, thus trading at $50/share. If both companies increase their EPS by $1, to $6, and the P/Es remain the same, that means company ABC rises to $30, and company XYZ rises to $60. Hey! One went up $5, and the other $10, twice as much! That means XYZ was the better investment, right? Nope. You see, shares are not tokens, and you don't get an identical, arbitrary number of them. You make an investment, and that's in dollars. So, say you'd invested $1,000 in each. $1,000 in ABC buys you 40 shares. $1,000 in XYZ buys you 20 shares. Their EPS adds that buck, the shares rise to maintain P/E, and you have: ABC: $6 EPS at P/E 5 = $30/share. Position value = 40 shares x $30/share = $1,200 XYZ: $6 EPS at P/E 10 = $60/share. Position value = 20 shares x $60/share = $1,200 They both make you the exact same 20% profit. It makes sense when you think about it this way: a 20% increase in EPS is going to give you a 20% increase in price if the P/E is to remain constant. It doesn't matter what the dollar amount of the EPS or the share price is." "What you need to do is go to yahoo finance and look at different stock's P/E ratios. You'll quickly see that the stocks can be sorted by this number. It would be an interesting exercise to get an idea of why P/E isn't a fixed number, how certain industries cluster around a certain number, but even this isn't precise. But, it will give you an idea as to why your question has no answer. ""Annual earnings are $1. What is the share price?"" ""Question has no answer""" This is only a rule of thumb. Peter Lynch popularized it; the ratio PE/growth is often called the Lynch Ratio. At best it's a very rough guideline. I could fill up this page with other caveats. I'm not saying that it's wrong, only that it's grossly incomplete. For a 10 second eyeball valuation of growth stocks, it's fine. But that's the extent of its usefulness. PE can be misleading when theres a good risk the company simply goes out of business in a few years. For this reason some people use PEG, which incorporates growth into the equation. generally Forward P/E is computed as current price / forward earnings.  The rationale behind this is that buying the stock costs you the current price, and it gives you a claim on the future earnings. "the ""how"" all depends on your level of computer savvy. Are you an Excel spreadsheet user or can you write in programming languages such as python? Either approach have math functions that make the calculation of ROI and Volatility trivial. If you're a python coder, then look up ""pandas"" (http://pandas.pydata.org/) - it handles a lot of the book-keeping and downloading of end of day equities data. With a dozen lines of code, you can compute ROI and volatility." The idea here is to get an idea of how to value each business and thus normalize how highly prized is each dollar that a company makes.  While some companies may make millions and others make billions, how does one put these in proper context?  One way is to consider a dollar in earnings for the company.  How does a dollar in earnings for Google compare to a dollar for Coca-cola for example?  Some companies may be valued much higher than others and this is a way to see that as share price alone can be rather misleading since some companies can have millions of shares outstanding and split the shares to keep the share price in a certain range. Thus the idea isn't that an investor is paying for a dollar of earnings but rather how is that perceived as some companies may not have earnings and yet still be traded as start-ups and other companies may be running at a loss and thus the P/E isn't even meaningful in this case. Assuming everything but the P/E is the same, the lower P/E would represent a greater value in a sense, yes.  However, earnings growth rate can account for higher P/Es for some companies as if a company is expected to grow at 40% for a few years it may have a higher P/E than a company growing earnings at 5% for example. The intrinsic value of a company is based on their profits year on year along with their expect future growth. A company may be posting losses, but if the market determines there's any chance they will turn a profit one day, or be a takeover target, it assigns value to those shares. In normal times, you'll observe a certain P/E range. Price to earning ratio is a simple way to say the I will pay X$ for a dollar's worth of earnings. A company that's in a flat market and not growing may command a P/E of only 10. Another company that's expanding their products and increasing market share may see a 20 P/E. Both P/Es are right for the type of company involved. One problem is that P/E ratio only looks at the last announced earnings. Let's take your manufacturing plant with a P/E of 12.5. Then they announce a major problem that will hurt future earnings and the price drops in half. Now the P/E is 6.25. It looks great, but since there aren't any new earnings that reflect the problem, it's very misleading.