How to calculate Price/Earnings - Price/Sales - Price/Free Cash Flow for given stock
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
The main question is, how much money you want to make?  With every transaction, you  should calculate the real price as the price plus costs. For example, if you but 10 GreatCorp stock of £100 each, and the transaction cost is £20 , then the real cost of buying a single share is in fact buying price of stock + broker costs / amount bought, or £104 in this case.  Now you want to make a profit so calculate your desired profit margin. You want to receive a sales price of buying price + profit margin + broker costs / amount bought. Suppose that you'd like 5%, then you'll need the price per stock of my example to increase to 100 + 5% + £40 / 10 = £109.  So you it only becomes worth while if you feel confident that GreatCorp's stock  will rise to that level. Read the yearly balance of that company to see if they don't have any debt, and are profitable. Look at their dividend earning history. Study the stock's candle graphs of the last ten years or so, to find out if there's no seasonal effects, and if the stock performs well overall. Get to know the company well. You should only buy GreatCorp shares after doing your homework.  But what about switching to another stock of LovelyInc? Actually it doesn't matter, since it's best to separate transactions. Sell your GreatCorp's stock when it has reached the desired profit margin or if it seems it is underperforming. Cut your losses! Make the calculations for LovelyCorp's shares without reference to GreatCorp's, and decide like that if it's worth while to buy. 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. :) "To add to @keshlam's answer slightly a stock's price is made up of several components: the only one of these that is known even remotely accurately at any time is the book value on the day that the accounts are prepared. Even  completed cashflows after the books have been prepared contain some slight unknowns as they may be reversed if stock is returned, for example, or reduced by unforeseen costs.  Future cashflows are based on (amongst other things) how many sales you expect to make in the future for all time. Exercise for the reader: how many iPhone 22s will apple sell in 2029? Even known future cashflows have some risk attached to them; customers may not pay for goods, a supplier may go into liquidation and so need to change its invoicing strategy etc.. Estimating the risk on future cashflows is highly subjective and depends greatly on what the analyst expects the exact economic state of the world will be in the future. Investors have the choice of investing in a risk free instrument (this is usually taken as being modelled by the 10 year US treasury bond) that is guaranteed to give them a return. To invest in anything riskier than the risk free instrument they must be paid a premium over the risk free return that they would get from that. The risk premium is related to how likely they think it is that they will not receive a return higher than that rate. Calculation of that premium is highly subjective; if I know the management of the company well I will be inclined to think that the investment is far less risky (or perhaps riskier...) than someone who does not, for example. Since none of the factors that go into a share price are accurately measurable and many are subjective there is no ""right"" share price at any time, let alone at time of IPO. Each investor will estimate these values differently and so value the shares differently and their trading, based on their ever changing estimates, will move the share price to an indeterminable level. In comments to @keshlam's answer you ask if there is enough information to work out the share price if a company buys out the company before IPO. Dividing the price that this other company paid by the relative ownership structure of the firm would give you an idea of what that company thought that the company was worth at that moment in time and can be used as a surrogate for market price but it will not and cannot accurately represent the market price as other investors will value the firm differently by estimating the criteria above differently and so will move the share price based on their valuation." P/E = price per earnings. low P/E (P/E < 4) means stock is undervalued. "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." It seems like you want to compare the company's values not necessarily the stock price.  Why not get the total outstanding shares and the stock price, generate the market cap.  Then you could compare changes to market cap rather than just share price. The average price would be $125 which would be used to compute your basis. You paid $12,500 for the stock that is now worth $4,500 which is a loss of $8,000 overall if you sell at this point. "Will the investment bank evaluate the worth of my company more than or less than 50 crs. Assuming the salvage value of the assets of 50 crs (meaning that's what you could sell them for to someone else), that would be the minimum value of your company (less any outstanding debts). There are many ways to calculate the ""value"" of a company, but the most common one is to look at the future potential for generating cash.   The underwriters will look at what your current cash flow projections are, and what they will be when you invest the proceeds from the public offering back into the company.  That will then be used to determine the total value of the company, and in turn the value of the portion that you are taking public. And what will be the owner’s share in the resulting public company? That's completely up to you.  You're essentially selling a part of the company in order to bring cash in, presumably to invest in assets that will generate more cash in the future.  If you want to keep complete control of the company, then you'll want to sell less than 50% of the company, otherwise you can sell as much or as little as you want." This is fine, but I'd probably spend a moment introducing WACC and it's estimation. It's also useful to link up the enterprise value to share price, so just also mentioning the debt subtraction to get equity value and division by shares for price.  Keep in mind you're usually given like a minute to answer this, so you can afford to be a bit more detailed in some parts. "Their algorithm may be different (and proprietary), but how I would to it is to assume that daily changes in the stock are distributed normally (meaning the probability distribution is a ""bell curve"" - the green area in your chart).  I would then calculate the average and standard deviation (volatility) of historical returns to determine the center and width of the bell curve (calibrating it to expected returns and implied volaility based on option prices), then use standard formulas for lognormal distributions to calculate the probability of the price exceeding the strike price. So there are many assumptions involved, and in the end it's just a probability, so there's no way to know if it's right or wrong - either the stock will cross the strike or it won't." If the company reported a loss at the previous quarter when the stock what at say $20/share, and now just before the company's next quarterly report, the stock trades around $10/share. There is a misunderstanding here, the company doesn't sell stock, they sell products (or services). Stock/share traded at equity market. Here is the illustration/chronology to give you better insight:   Now addressing the question What if the stock's price change? Let say, Its drop from $10 to $1 Is it affect XYZ revenue ? No why? because XYZ selling ads not their stocks the formula for revenue revenue = products (in this case: ads) * quantity the equation doesn't involve capital (stock's purchasing) Stock price = Earning per share * P/E Ratio. Most of the time you will see in a listing the Stock price and the P/E ration. The calculation of the EPS is left as an exercise for the student Investor. "(Value of shares+Dividends received)/(Initial investment) would be the typical formula though this is more of a percentage where 1 would indicate that you broke even, assuming no inflation to be factored. No, you don't have to estimate the share price based on revenues as I would question how well did anyone estimate what kind of revenues Facebook, Apple, or Google have had and will have. To estimate the value of shares, I'd likely consider what does my investment strategy use as metrics: Is it discounted cash flow, is it based on earnings, is it something else? There are many ways to determine what a stock ""should be worth"" that depending on what you want to believe there are more than a few ways one could go." Thanks for this, great in depth answer. I had previously calculated a WACC and have used it for my discount rate.   As part of your last point on revenue vs. cash, I've set a accounts receivable period of 30 days, and then applied a factor of 30/365 * revenue to understand what portion of my revenue is not cash in hand. Does that make sense? Too calculate these values, information contained in the company's financial statements (income, balance, or cashflow) will be needed along with the price.  Google finance does not maintain this information for BME.  You will need to find another source for this information or analyze another another symbol's financial section (BAC for example).