How can I figure out how a stock's price would change after I buy shares?
It is unlikely that buying 100 shares will have any effect on a stock's price, unless the stock's average trading volume is incredibly low.  That being said, no matter how many share you buy, there's no way to know what the impact on the price will be, because that's only one factor in how shares are priced.  If anyone could figure out the answer to your question then they'd be extremely rich, because they'd simply watch for big share trades and then buy those stocks on the way up. The market makers who actually execute the trades are the ones who set the prices, and most stocks have multiple market makers trading the stock, so the bid/ask you see is the highest bid and lowest ask.  The market makers set the price based on what the trend of the stock is.  If, for instance, there's a large number of sell orders against a stock, the market makers will start dropping the bid prices as they fill execution orders, and as they see buy orders increase, they'll raise ask prices as they fill execution orders.  The market makers earn the difference between what they paid to buy someone's stock who was selling and what they get from someone else who buys it. This is a simplified explanation, so pro traders, don't beat me up! (grin) So, basically, it takes quite a bit of share volume in one direction or another to affect a stock's price.  I can guarantee a 100-share trade wouldn't even be noticed by market makers. I hope this helps. Good luck! Stock price is based on supply and demand. Unless the stock you are looking to buy usually has very low volume trading 100 shares isn't likely to have any effect on price. There are many companies that have millions or tens of millions of shares trade daily. For stocks like that 100 shares is barely a trivial percentage of the daily volume. For thinly traded stocks you can look at the bid and ask size but even that isn't likely to get you an exact answer. Unless you are trading large volumes your trade will have no effect on the price of shares. It is possible to figure out the next price. Just not for Joe Average. A stock exchange has a orderbook. This has two sides. One side has alle the buyers, how many shares they want, and what they are willing to pay. The other side has all the sellers, how many shares they got, and what price they are willing to accept. If any buyers and sellers match up, their orders are executed, money and shares are exchanged, everyone is happy. So the current asking price (the price you have to pay, to get some shares) is currently 12.46$. Let's say you want 6000 shares, for any price. The orderbook now looks like this: Your order is executed, you get 6000 shares for a total of 74,761$ (5900 * 12,46 + 100 * 12,47$). The order book now looks like this: The new asking price is 12.47$. Congrats, you knew the price in advance. Of course this is simplified, there are millions of entries on both sides, thousands of trades happen every millisecond and you'll have to pay the stock exchange a lot of money to give you all this information in real time.  That's what high frequency traders are doing. They use highly specialised computer systems to exploit differences in stock exchanges all over the world. It's called arbitage. They have to be faster than the other guy. This race has gone on for a few years now, so that the limiting factor starts to become the speed of light. YOU are not going to benefit, or else you would not be asking questions on PERSONAL finance :) "It depends on many factors, but generally, the bid/ask spread will give you an idea. There are typically two ways to buy (or sell) a security: With a limit order, you would place a buy for 100 shares at $30-. Then it's easy, in the worst case you will get your 100 shares at $30 each exactly. You may get lucky and have the price fall, then you will pay less than $30. Of course if the price immediately goes up to say $35, nobody will sell at the $30 you want, so your broker will happily sit on his hands and rake in the commission while waiting on what is now a hail Mary ask. With a market order, you have the problem you mention: The ticker says $30, but say after you buy the first 5 shares at $30 the price shoots up and the rest are $32 each - you have now paid on average $31.9 per share. This could happen because there is a limit order for 5 at $30 and 200 at $32 (you would have filled only part of that 200). You would be able to see these in the order book (sometimes shown as bid/ask spread or market depth). However, the order book is not law. Just because there's an ask for 10k shares at $35 each for your $30 X stock, doesn't mean that by the time the price comes up to $35, the offer will still be up. The guy (or algorithm) who put it up may see the price going up and decide he now wants $40 each for his 10k shares. Also, people aren't obligated to put in their order: Maybe there's a trader who intends to trade a large volume when the price hits a certain level, like a limit order, but he elected to not put in a limit order and instead watch the ticker and react in real time. Then you will see a huge order suddenly come in out of nowhere. So while the order book is informative, what you are asking is actually fundamentally impossible to know fully, unless you can read the minds of every interested trader. As others said, in ""normal"" securities (meaning traded at a major exchange, especially those in the S&P500) you simply can't move the price, the market is too deep. You would need millions of dollars to budge the price, and if you had that much money, you wouldn't be asking here on a QA site, you would have a professional financial advisor (or even a team) that specializes in distributing your large transaction over a longer time to minimize the effect on the market. With crazier stocks, such as OTC and especially worthless penny stocks with market caps of $1 mil or less, what you say is a real problem (you can end up paying multiples of the last ticker if not careful) and you do have to be careful about it. Which is why you shouldn't trade penny stocks unless you know what you're doing (and if you're asking this question here, you don't)."
"Great question! While investing in individual stocks can be very useful as a learning experience, my opinion is that concentrating an entire portfolio in a few companies' stock is a mistake for most investors, and especially for a novice for several reasons. After all, only a handful of professional investors have ever beaten the market over the long term by picking stocks, so is it really worth trying? If you could, I'd say go work on Wall Street and good luck to you. Diversification For many investors, diversification is an important reason to use an ETF or index fund. If they were to focus on a few sectors or companies, it is more likely that they would have a lop-sided risk profile and might be subject to a larger downside risk potential than the market as a whole, i.e. ""don't put all your eggs in one basket"". Diversification is important because of the nature of compound investing - if you take a significant hit, it will take you a long time to recover because all of your future gains are building off of a smaller base. This is one reason that younger investors often take a larger position in equities, as they have longer to recover from significant market declines. While it is very possible to build a balanced, diversified portfolio from individual stocks, this isn't something I'd recommend for a new investor and would require a substantial college-level understanding of investments, and in any case, this portfolio would have a more discrete efficient frontier than the market as a whole. Lower Volatility Picking individual stocks or sectors would could also significantly increase or decrease the overall volatility of the portfolio relative to the market, especially if the stocks are highly cyclical or correlated to the same market factors. So if they are buying tech stocks, they might see bigger upswings and downswings compared to the market as a whole, or see the opposite effect in the case of utilities. In other words, owning a basket of individual stocks may result in an unintended volatility/beta profile. Lower Trading Costs and Taxes Investors who buy individual stocks tend to trade more in an attempt to beat the market. After accounting for commission fees, transaction costs (bid/ask spread), and taxes, most individual investors get only a fraction of the market average return. One famous academic study finds that investors who trade more trail the stock market more. Trading also tends to incur higher taxes since short term gains (<1 year) are taxed at marginal income tax rates that are higher than long term capital gains. Investors tend to trade due to behavioral failures such as trying to time the market, being overconfident, speculating on stocks instead of long-term investing, following what everyone else is doing, and getting in and out of the market as a result of an emotional reaction to volatility (ie buying when stocks are high/rising and selling when they are low/falling). Investing in index funds can involve minimal fees and discourages behavior that causes investors to incur excessive trading costs. This can make a big difference over the long run as extra costs and taxes compound significantly over time. It's Hard to Beat the Market since Markets are Quite Efficient Another reason to use funds is that it is reasonable to assume that at any point in time, the market does a fairly good job of pricing securities based on all known information. In other words, if a given stock is trading at a low P/E relative to the market, the market as a whole has decided that there is good reason for this valuation. This idea is based on the assumption that there are already so many professional analysts and traders looking for arbitrage opportunities that few such opportunities exist, and where they do exist, persist for only a short time. If you accept this theory generally (obviously, the market is not perfect), there is very little in the way of insight on pricing that the average novice investor could provide given limited knowledge of the markets and only a few hours of research. It might be more likely that opportunities identified by the novice would reflect omissions of relevant information. Trying to make money in this way then becomes a bet that other informed, professional investors are wrong and you are right (options traders, for example). Prices are Unpredictable (Behave Like ""Random"" Walks) If you want to make money as a long-term investor/owner rather than a speculator/trader, than most of the future change in asset prices will be a result of future events and information that is not yet known. Since no one knows how the world will change or who will be tomorrow's winners or losers, much less in 30 years, this is sometimes referred to as a ""random walk."" You can point to fundamental analysis and say ""X company has great free cash flow, so I will invest in them"", but ultimately, the problem with this type of analysis is that everyone else has already done it too. For example, Warren Buffett famously already knows the price at which he'd buy every company he's interested in buying. When everyone else can do the same analysis as you, the price already reflects the market's take on that public information (Efficent Market theory), and what is left is the unknown (I wouldn't use the term ""random""). Overall, I think there is simply a very large potential for an individual investor to make a few mistakes with individual stocks over 20+ years that will really cost a lot, and I think most investors want a balance of risk and return versus the largest possible return, and don't have an interest in developing a professional knowledge of stocks. I think a better strategy for most investors is to share in the future profits of companies buy holding a well-diversified portfolio for the long term and to avoid making a large number of decisions about which stocks to own." The same applies if you were looking for a business to buy: would you pay more for a business that is doing well making increasing profits year after year, or for a business that is not doing so well and is losing money. A share in a company is basically a small part of a company which a shareholder can own. So would you rather own a part of a company that is increasing profits year after year or one that is continuously losing money? Someone would buy shares in a company in order to make a better return than they could make elsewhere. They can make a profit through two ways: first, a share of the company's profits through dividends, and second capital gains from the price of the shares going up. Why does the price of the shares go up over the long term when a company does well and increases profits? Because when a company increases profits they are making more and more money which increases the net worth of the company. More investors would prefer to buy shares in a company that makes increasing profits because this will increase the net worth of the company, and in turn will drive the share price higher over the long term. A company's increase in profits creates higher demand for the company's shares. Think about it, if interest rates are so low like they are now, where it is hard to get a return higher than inflation, why wouldn't investors then search for higher returns in good performing companies in the stock market? More investors' and traders' wanting some of the pie, creates higher demand for good performing stocks driving the share price higher. The demand for these companies is there primarily because the companies are increasing their profits and net worth, so over the long term the share price will increase in-line with the net worth. Over the short to medium term other factors can also affect the share price, sometime opposite to how the company is actually performing; however this is a whole different answer to a whole different question. "Most of the answers here reflect a misunderstanding of what gold actually is from a financial perspective.  I'll answer your question by asking two questions, and I do challenge you to stop and think about what we mean when we say ""cash"" or ""unit of exchange"" because without understanding those, you will completely miss this answer. In 1971, the DXY was 110.  For people who don't know, the DXY is the US Dollar Index - it weighs the strength of the US Dollar relative to other currencies.  Hey look, it's a pretty graph of the DXY's history. In 1971, gold was $35 an ounce. The DXY is 97 today. Gold is $1170 an ounce today. Now the questions: If shares of Company A in 1971 were $10 a share, but now are $100 a share and some of this is because the company has grown, but some of it is because of inflation and the DXY losing value, what would the value of the company be if it was held in grams of gold and not dollars? Benjamin Graham, who influenced Warren Buffett, is a ""supposed"" critic of gold, yet what percent of his life were we not on a gold standard?  In his day, the dollar was backed by gold - why would you buy gold if every dollar represented gold. Finally, consider how many US Dollars exist, and how few metric tonnes of gold exist (165,000).  Even Paul Volcker admitted that a new gold standard would be impossible because the value of gold, if we did it today, would put gold in the $5000-$10000 range - which is absurd: To get on a gold standard technically now, an old fashioned gold   standard, and you had to replace all the dollars out there in foreign   hands with gold, God the price, you buy gold, because the price of   gold would have to be enormous. So, you're all left hoping the Federal Reserve figures how to get us all out of this mess without causing trouble, otherwise, let me just kindly say, you WILL realize the value of gold then. As the old saying goes, ""A fool and his money are soon parted.""  I could be wrong, but I'd say that those who've been buying gold since 1971 for their ""cash holdings"" (not index funds) aren't the suckers." "When we say ""stock market,"" we are usually thinking of the publicly traded stocks, such as the New York Stock Exchange or the NASDAQ. Shares of individual products do not go on these exchanges, only large corporations.  You won't see a stock ticker symbol for The Force Awakens or for the iPhone 6s Plus.  The reason for this is that when investors buy a stock, they are looking for something that will grow in value theoretically forever. Individual products usually have a limited lifespan. Your movie will (hopefully) generate revenue when it comes out, but after a while sales will slow down after people have seen it. If someone bought a share of stock in a movie on the stock market, they have to realize that eventually the movie will stop making money, and their share of stock won't be worth anything anymore. Instead, people invest in companies that have the potential to make new products, such as Disney or Apple.  So if you were envisioning seeing the ticker symbol of your movie going across the screen on CNBC, sorry, that's not going to happen.  However, you could theoretically sell shares to individual investors for a percentage of the profit. You figure out how much money you need to create the movie, and estimate how much profit you think the movie will earn. Then you find an investor (or group of investors) that is willing to give you the money you need in exchange for a percentage of the profit. Unlike a stock market investor, these investors won't be looking for the long-term growth potential of the resale value of the stock, but simply a share of the profit." If you buy for $1 and sell $1 when the price goes to $2, you would have sold only half of your initial investment. So your investment would now be worth $2 and you sell $1 leaving $1 still in the market.  This means you would have sold half your initial investment, making a profit of $0.50 on this half of your initial investment, and having to pay CGT on this amount. "There are two scenarios to determine the relevant date, and then a couple of options to determine the relevant price. If the stocks were purchased in your name from the start - then the relevant date is the date of the purchase. If the stocks were willed to you (i.e.: you inherited them), then the relevant date is the date at which the person who willed them to you had died. You can check with the company if they have records of the original purchase. If it was in ""street name"" - they may not have such records, and then you need to figure out what broker it was to hold them. Once you  figured out the relevant date, contact the company's ""investor relationships"" contact and ask them for the adjusted stock price on that date (adjusted for splits/mergers/acquisitions/whatever). That would be the cost basis per share you would be using. Alternatively you can research historical prices on your favorite financial information site (Google/Yahoo/Bloomberg or the stock exchange where the company is listed). If you cannot figure the cost basis, or it costs too much - you can just write cost basis as $0, and claim the whole proceeds as gains. You'll pay capital gains tax on the whole amount, but that may end up being cheaper than conducting the investigation to reveal the actual numbers." 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. "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."