Does negative P/E ratio mean stock is weak?
P/E is the number of years it would take for the company to earn its share price.  You take share price divided by annual earnings per share.  You can take the current reported quarterly earnings per share times 4, you can take the sum of the past four actual quarters earnings per share or you can take some projected earnings per share. It has little to do with a company's actual finances apart from the earnings per share.  It doesn't say much about the health of a company's balance sheet, and is definitely not an indicator for bankruptcy.  It's mostly a measure of the market's assumptions of the company's ability to grow earnings or maintain it's current earnings growth.   A share price of $40 trading for a P/E ratio of 10 means it will take the company 10 years to earn $40 per share, it means there's current annual earnings per share of $4.  A different company may also be earning $4 per share but trade at 100 times earnings for a share price of $400.  By this measure alone neither company is more or less healthy than the other.  One just commands more faith in the future growth from the market. To circle back to your question regarding a negative P/E, a negative P/E ratio means the company is reporting negative earnings (running at a loss).  Again, this may or may not indicate an imminent bankruptcy.  Increasing balance sheet debt with decreasing revenue and or earnings and or balance sheet assets will be a better way to assess bankruptcy risk.
I look at the following ratios and how these ratios developed over time, for instance how did valuation come down in a recession, what was the trough multiple during the Lehman crisis in 2008, how did a recession or good economy affect profitability of the company. Valuation metrics: Enterprise value / EBIT (EBIT = operating income) Enterprise value / sales (for fast growing companies as their operating profit is expected to be realized later in time) and P/E Profitability: Operating margin, which is EBIT / sales Cashflow / sales Business model stability and news flow 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: There are books on the subject of valuing stocks. P/E ratio has nothing directly to do with the value of a company. It may be an indication that the stock is undervalued or overvalued, but does not indicate the value itself. The direct value of company is what it would fetch if it was liquidated. For example, if you bought a dry cleaner and sold all of the equipment and receivables, how much would you get? To value a living company, you can treat it like a bond. For example, assume the company generates $1 million in profit every year and has a liquidation value of $2 million. Given the risk profile of the business, let's say we would like to make 8% on average per year, then the value of the business is approximately $1/0.08 + $2 = $14.5 million to us. To someone who expects to make more or less the value might be different. If the company has growth potential, you can adjust this figure by estimating the estimated income at different percentage chances of growth and decline, a growth curve so to speak. The value is then the net area under this curve.  Of course, if you do this for NYSE and most NASDAQ stocks you will find that they have a capitalization way over these amounts. That is because they are being used as a store of wealth. People are buying the stocks just as a way to store money, not necessarily make a profit. It's kind of like buying land. Even though the land may never give you a penny of profit, you know you can always sell it and get your money back. Because of this, it is difficult to value high-profile equities. You are dealing with human psychology, not pennies and dollars. But they beat most revenue estimates... should be a heavy down day tomorrow, even though the stock is already massively oversold, especially when compared to industry peers and average P/E ratios of tech companies.  Last 12 months of earnings: $44.16 There are 2 primary ways to bet against a stock if you think it will decline. The first is to short sell shares of that stock the second is to buy put options (I would also add that selling naked call options would also be a bet against but I don't believe that is as common as the other 2 mentioned methods). The problem with short selling an IPO is that you first have to borrow the shares you are going to sell. Since the shares are privately held prior to the IPO that can be problematic. Even after the IPO you may have to wait a bit before shares become available to borrow.  The problem with options (either buying puts or seeking naked calls) is similar. Options are traded on a different exchange than the stock and they have their own requirements that a stock must meet to have options traded. Both of these problems eventually correct themselves however, not in time for you to catch the initial fall you seem to be looking for. "There are two common types of P/E ratio calculations: ""trailing"" and ""forward"" (and then there are various mixes of the two). Trailing P/E ratios are calculated as [current price] / [trailing 12-month EPS]. An alternative is the Forward P/E ratio, which is based on an estimate of earnings in the coming 12 months. The estimate used is usually called ""consensus"" and, to answer your question, is the average estimate of analysts who cover the stock. Any reputable organization will disclose how they calculate their financials. For example, Reuters uses a trailing ratio (indicated by ""TTM"") on their page for BHP. So, the first reason a PE ratio might not jump on an announcement is it might be forward looking and therefore not very sensitive to the realized earnings. The second reason is that if it is a trailing ratio, some of the annual EPS change is known prior to the annual announcement. For example, on 12/31 a company might report a large drop in annual earnings, but if the bulk of that loss was reported in a previous quarterly report, then the trailing EPS would account partially for it prior to the annual announcement.  In this case, I think the first reason is the culprit. The Reuters P/E of nearly 12 is a trailing ratio, so if you see 8 I'd think it must be based on a forward-looking estimate." It's been traded publicly for only about a month.  I wouldn't put much credence in a P/E ratio just yet because it hasn't had to report anything like a grown-up publicly traded company yet. They haven't been doing very well for a while. Their stock was in a downward trend since October 2006. They had an upward trend since 1986, then in 2006 they transitioned to a downward slope. Their stock plummeted in 2008, then rebounded shortly after (due to the bailout?) to continue its downward trend.