What is the formula for determining estimated stock price when I  only have an earning per share number?
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. "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""" See this link...I was also looking an answer to the same questions. This site explains with an example  http://www.independent-stock-investing.com/PE-Ratio.html
Are you implying that Amazon is a better investment than GE because Amazon's P/E is 175 while GE's is only 27?  Or that GE is a better investment than Apple because Apple's P/E is just 13.  There are a lot of other ratios to consider than P/E.  I personally view high P/E numbers as a red flag.  One way to think of a P/E ratio is the number of years it's expected for the company to earn its market cap.  (Share price divided by annual earnings per share)  It will take Amazon 175 years to earn $353 billion. If I was going to buy a dry cleaners, I would not pay the owner 175 years of earnings to take control of it, I'd never see my investment back. To your point.  There is so much future growth seemingly built in to today's stock market that even when a company posts higher than expected earnings, the company's stock may take a hit because maybe future prospects are a little less bright than everyone thought yesterday. The point of fundamental analysis is that you want to look at a company's management style and financial strategies.  How is it paying its debt?  How is it accumulating the debt?  How is it's return on assets?  How is the return on assets trending?  This way when you look at a few companies in the same market segment you may have a better shot at picking the winner over time.  The company that piles on new debt for every new project is likely to continue that path in to oblivion, regardless of the P/E ratio. (or some other equally less forward thinking management practice that you uncover in your fundamental analysis efforts). And I'll add... No amount of historical good decision making from a company's management can prepare for a total market downturn, or lack of investor confidence in general.  The market is the market; sometimes it's up irrationally, sometimes it's down irrationally. What I do have is this (sample only): Stock X: Average Price of all I purchased before = 80 Total Shares = 200 So if Stock X's price today is 100 how do I know how much my average price will be? Using your sample if you buy 100 new shares and the price is 85 for the purpose of this example your previous total cost is $16,000 ($80 average cost * 200 shares).  With the new example you are adding $8500 to your total cost (100 new shares * $85 example cost per share)  that gives us a total cost of $24,500 and 300 shares. $24,500/300 gives us an average cost of $81.67 per share. As long as you have the average cost and the number of shares you can calculate a new average without knowing what the price was for each transaction. It may still become important to find the price information for tax purposes if you do not sell all of those shares at once and use FIFO for your taxes. "I think you've got basics, but you may have the order / emphasis a bit wrong. I've changed the order of the things you've learned in to what I think is the most important to understand: Owning a stock is like owning a tiny chunk of the business Owning stock is owning a tiny chunk of the business, it's not just ""like"" it. The ""tiny chunks"" are called shares, because that is literally what they are, a share of the business. Sometimes shares are also called stocks. The words stock and share are mostly interchangeable, but a single stock normally means your holding of many shares in a business, so if you have 100 shares in 1 company, that's a stock in that company, if you then buy 100 shares in another company, you now own 2 stocks. An investor seeks to buy stocks at a low price, and sell when the price is high. Not necessarily. An investor will buy shares in a company that they believe will make them a profit. In general, a company will make a profit and distribute some or all of it to shareholders in the form of dividends. They will also keep back a portion of the profit to invest in growing the company. If the company does grow, it will grow in value and your shares will get more valuable. Price (of a stock) is affected by supply/demand, volume, and possibly company profits The price of a share that you see on a stock ticker is the price that people on the market have exchanged the share for recently, not the price you or I can buy a share for, although usually if people on the market are buying and selling at that price, someone will buy or sell from you at a similar sort of price. In theory, the price will be the companies total value, if you were to own the whole thing (it's market capitalisation) divided by the total number of shares that exist in that company. The problem is that it's very difficult to work out the total value of a company. You can start by counting the different things that it owns (including things like intellectual property and the knowledge and experience of people who work there), subtract all the money it owes in loans etc., and then make an allowance for how much profit you expect the company to make in the future. The problem is that these numbers are all going to be estimates, and different peoples estimates will disagree. Some people don't bother to estimate at all. The market makers will just follow supply and demand. They will hold a few shares in each of many companies that they are interested in. They will advertise a lower price that they are willing to buy at and a higher price that they will sell at all the time. When they hold a lot of a share, they will price it lower so that people buy it from them. When they start to run out, they will price it higher. You will never need to spend more than the market makers price to buy a share, or get less than the market makers price when you come to sell it (unless you want to buy or sell more shares than they are willing to). This is why stock price depends on supply and demand. The other category of people who don't care about the companies they are trading are the high speed traders. They just look at information like the past price, the volume (total amount of shares being exchanged on the market) and many other statistics both from the market and elsewhere and look for patterns. You cannot compete with these people - they do things like physically locate their servers nearer to the stock exchanges buildings to get a few milliseconds time advantage over their competitors to buy shares quicker than them." "What does it mean in terms of share price? Should the share price increase by 15 cents?  No, but you're on the right track. In theory, the price of a share reflects it's ""share"" of time discounted future earnings. To put it concretely, imagine a company consistently earning 15 cents a share every year and paying it all out as dividends. If you only paid 25 cents for it, you could earn five cents a share by just holding it for two years. If you imagine that stocks are priced assuming a holding period of 20 years or so, so we'd expect the stock to cost less than 3 dollars.  More accurately, the share price reflects expected future earnings. If everyone is assuming this company is growing earnings every quarter, an announcement will only confirm information people have already been trading based on. So if this 15 cents announcement is a surprise, then we'd expect the stock price to rise as a function of both the ""surprise"" in earnings, and how long we expect them to stay at this new profitability level before competition claws their earnings away. Concretely, if 5 cents a share of that announcement were ""earnings surprise,"" you'd expect it to rise somewhere around a dollar." Thank you very much for this thoughtful response.  In my opinion the judges care more about the why behind your valuation rather than a how.  Anyone can use a formula, but it takes so much more to understand why to use the formula.    Personally, the 'why' is going to be the toughest part for me understand and wrap my head around.  Once again thank you for the advice and the tip. Usually their PE ratio will just be listed as 0 or blank.  Though I've always wondered why they don't just list the negative PE as from a straight math standpoint it makes sense. PE while it can be a useful barometer for a company, but certainly does not tell you everything.  A company could have negative earnings for a lot of reasons, some good and some bad.  The company could just be a bad company and could be losing money hand over fist, or the company could have had a one time occurrence such as a big acquisition or some other event that just affected this years earnings, or they could be an awesome high growth company that is heavily investing for their future and forgoing locking in profits now for much bigger profits in the future. Generally IPO company's fall into that last category as they are going public usually because they want an influx of cash that they are going to use to grow the company much more rapidly.  So they are likely already taking all incoming $$ and taking on debt to grow the company and have exceeded all of those options and that's when they turn to the stock market for the additional influx of cash, so it is very common for these companies not to have earnings.   Now you just have to decide if that company is investing that money wisely and will in the future translate to actual earnings. As yet another explanation of why it does not really matter, you can look at this from the valuation point of view. Stock price is the present value of its future cash flows (be it free cash flow of the firm or dividends, depending on the model). Let's have a look at the dividends case. Imagine, the price of the stock is based on only three dividends streams $5 dollars each: dividend to be paid today, in year 1, and in year 2. Each should be discounted back to today (say, at 10%), except today's dividend, since today is now.  Once that dividend is paid, it is no longer in the stream of cash flows. So if we just delete that first $5 from the formula, the price will adjust itself down by the amount of the dividend to $8.68. NOTE that this is a very simple example, since in reality cash flows streams are arguably infinite and because there are many other factors affecting stock price. But simply for your understanding, this example should provide you with the reason simply from the valuation perspective. Really not sure with this one and I don't want to cheat and look up an answer.  I'd say you could find the high/low points of the stock over the last year or two and see how large the spread is between those values and the average price of the stock over the same time period.