Numbers can lie -- yet they're the best first step in determining whether a stock is a buy. In this series, we use some carefully chosen metrics to size up a stock's true value based on the following clues:

  • The current price multiples.
  • The consistency of past earnings and cash flow.
  • How much growth we can expect.

Let's see what those numbers can tell us about how expensive or cheap Intuitive Surgical (Nasdaq: ISRG) might be.

The current price multiples
First, we'll look at most investors' favorite metric: the P/E ratio. It divides the company's share price by its earnings per share (EPS) -- the lower, the better.

Then we'll take things up a notch with a more advanced metric: enterprise value to unlevered free cash flow, which divides the company's enterprise value (basically, its market cap plus its debt, minus its cash) by its unlevered free cash flow (its free cash flow, adding back the interest payments on its debt). As with the P/E, the lower this number is, the better.

Analysts argue about which is more important -- earnings or cash flow. Who cares? A good buy ideally has low multiples on both.

Intuitive Surgical has a P/E ratio of 37.6 and an EV/FCF ratio of 33.5 over the trailing 12 months. If we stretch and compare current valuations with the five-year averages for earnings and free cash flow, we see that Intuitive Surgical has a P/E ratio of 65.7 and a five-year EV/FCF ratio of 54.4.

A positive one-year ratio of less than 10 for both metrics is ideal (at least in my opinion). For a five-year metric, less than 20 is ideal.

Intuitive Surgical is 0-for-4 on hitting the ideal targets, but let's see how it stacks up against some of its competitors and industry mates (MAKO Surgical may be the best comp, but I excluded it here because none of its price multiples are meaningful because of losses). 

Company

1-Year P/E

1-Year EV/FCF

5-Year P/E

5-Year EV/FCF

Intuitive Surgical 37.6 33.5 65.7 54.4
Medtronic (NYSE: MDT) 12.0 11.7 13.7 13.0
Stryker (NYSE: SYK) 15.3 15.2 16.6 15.6
CR Bard (NYSE: BCR) 21.5 11.4 18.6 14.1

Source: S&P Capital IQ; NM = not meaningful because of losses.

Numerically, we've seen how Intuitive Surgical's valuation rates on both an absolute and relative basis. Next, let's examine ...

The consistency of past earnings and cash flow
An ideal company will be consistently strong in its earnings and cash-flow generation.

In the past five years, Intuitive Surgical's net income margin has ranged from 21.4% to 28.2%. In that same time frame, unlevered free cash flow margin has ranged from 21.4% to 31.6%.

How do those figures compare with those of the company's peers? See for yourself:

Isrg

Source: S&P Capital IQ; margin ranges are combined.

In addition, over the past five years, Intuitive Surgical has tallied up five years of positive earnings and five years of positive free cash flow.

Next, let's figure out ...

How much growth we can expect
Analysts tend to comically overstate their five-year growth estimates. If you accept them at face value, you will overpay for stocks. But even though you should definitely take the analysts' prognostications with a grain of salt, they can still provide a useful starting point when compared with similar numbers from a company's closest rivals.

Let's start by seeing what this company's done over the past five years. In that time period, Intuitive Surgical has put up past EPS growth rates of 35%. Meanwhile, Wall Street's analysts expect future growth rates of 19.7%.

Here's how Intuitive Surgical compares with its peers for trailing-five-year growth:

Isrg

Source: S&P Capital IQ; EPS growth shown.

And here's how it measures up with regard to the growth analysts expect over the next five years:

Isrg

Source: S&P Capital IQ; estimates for EPS growth.

The bottom line
The pile of numbers we've plowed through has shown us the price multiples that shares of Intuitive Surgical are trading at, the volatility of its operational performance, and what kind of growth profile it has -- both on an absolute and a relative basis.

The more consistent a company's performance has been and the more growth we can expect, the more we should be willing to pay. We've gone well beyond looking at a 37.6 P/E ratio, and we see that Intuitive Surgical is a profitable growth stock. It sells for high price multiples, but it shows high margins and high past and expected future growth. I continue to hold Intuitive Surgical because I like its proven profitability and the potential of robotic surgery.

I bought in on a dip a few years ago, and my bar for holding is lower than purchasing shares at today's price, but Intuitive Surgical is currently a "Best Buy Now" of our Motley Fool Rule Breakers newsletter service (so is MAKO Surgical). If you find Intuitive Surgical's numbers or story compelling, don't stop here. Continue your due-diligence process until you're confident one way or the other. As a start, add it to My Watchlist to find all of our Foolish analysis.

You can also see the stocks that I've researched beyond the initial numbers and bought in my public real-money portfolio.