How a financial analyst calculate the price to buy or sell a stock?

The value of a company is defined as the net present value of future cashflows. Analysts estimate the future cashflows of a company, then estimate an interest rate to discount those cashflows to the present and figure out what they are worth now. (discounted cashflow) The interest rate used to discount the cashflows corresponds to the risk of a stock and the rate of return needed to maintain the value of the company. They estimate multiples, like the P/E ratio, price to book, price to sales. price to cashflow etc. and growth rates to to estimate a price target. Its like predicting the weather or anything else in the future. You never know whats going to happen in the future. Sometimes you're right and sometimes you are wrong.

There are several ways to select a stock to buy:

1. Fundamentally compare stocks in an industry against others in the same industry, then buy the one with the best stats.
2. Fundamentally figure the stocks current hypothetical value based on all known facts. Real-time values, not accounting numbers, which may show written down numbers or values based on the lower cost rather than current market value off the balance sheet.Compare stocks real-time book value to its accounting book value. Buy ones where real-time BV exceeds accounting value.
3. establish a hypothetical trend for for the stock price growth considering such things as projected change in market share, new predict pipeline, projected growth in revenue and earnings, then pick the best growth expectation.

For a sell target, estimate the average P/e ratio for the company then multiply by your estimated earnings per share for a growth situation.
For a value situation, when the stock price divided by your estimated book value exceeds the stocks average 10 year price to book ratio.
There is obviously more to it than can be explained in a few sentences, but this is the framework we use.

Financial analysts usually have no idea what they're talking about, so their estimates are way off most of the time. They're always revising them.

But, the methodology is generally to project future earnings/sales. How to do that is kind of unclear but generally you look at past performance and estimate a growth rate. It's just a big spreadsheet really. After you get the value of the company, you figure out what their stock is using a variety of methods. One popular one is P/E ratios, where they can calculate a price based on current/historical P/E ratios.