Under Armour, Inc. (NYSE:UAA) shares have continued their recent momentum with a 31% gain in the last month alone. Looking back a bit further, it's encouraging to see the stock is up 55% in the last year.

Although its price has surged higher, it's still not a stretch to say that Under Armour's price-to-sales (or "P/S") ratio of 0.9x right now seems quite "middle-of-the-road" compared to the Luxury industry in the United States, where the median P/S ratio is around 0.8x. While this might not raise any eyebrows, if the P/S ratio is not justified investors could be missing out on a potential opportunity or ignoring looming disappointment.

What Does Under Armour's P/S Mean For Shareholders?

Under Armour could be doing better as its revenue has been going backwards lately while most other companies have been seeing positive revenue growth. One possibility is that the P/S ratio is moderate because investors think this poor revenue performance will turn around. If not, then existing shareholders may be a little nervous about the viability of the share price.

What Are Revenue Growth Metrics Telling Us About The P/S?

In order to justify its P/S ratio, Under Armour would need to produce growth that's similar to the industry.

Taking a look back first, the company's revenue growth last year wasn't something to get excited about as it posted a disappointing decline of 5.2%. This has erased any of its gains during the last three years, with practically no change in revenue being achieved in total. Therefore, it's fair to say that revenue growth has been inconsistent recently for the company.

Looking ahead now, revenue is anticipated to slump, contracting by 0.2% each year during the coming three years according to the analysts following the company. That's not great when the rest of the industry is expected to grow by 6.5% per year.

In light of this, it's somewhat alarming that Under Armour's P/S sits in line with the majority of other companies. It seems most investors are hoping for a turnaround in the company's business prospects, but the analyst cohort is not so confident this will happen. Only the boldest would assume these prices are sustainable as these declining revenues are likely to weigh on the share price eventually.

What We Can Learn From Under Armour's P/S?

Its shares have lifted substantially and now Under Armour's P/S is back within range of the industry median. While the price-to-sales ratio shouldn't be the defining factor in whether you buy a stock or not, it's quite a capable barometer of revenue expectations.

It appears that Under Armour currently trades on a higher than expected P/S for a company whose revenues are forecast to decline. With this in mind, we don't feel the current P/S is justified as declining revenues are unlikely to support a more positive sentiment for long. If the poor revenue outlook tells us one thing, it's that these current price levels could be unsustainable.

And what about other risks? Every company has them, and we've spotted 1 warning sign for Under Armour you should know about.

It's important to make sure you look for a great company, not just the first idea you come across. So if growing profitability aligns with your idea of a great company, take a peek at this free list of interesting companies with strong recent earnings growth (and a low P/E).

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This article by Simply Wall St is general in nature. We provide commentary based on historical data and analyst forecasts only using an unbiased methodology and our articles are not intended to be financial advice. It does not constitute a recommendation to buy or sell any stock, and does not take account of your objectives, or your financial situation. We aim to bring you long-term focused analysis driven by fundamental data. Note that our analysis may not factor in the latest price-sensitive company announcements or qualitative material. Simply Wall St has no position in any stocks mentioned.