Apple (NASDAQ:AAPL) has just put a date to its fiscal third-quarter earnings release: July 30, after the market close. That report will follow two straight quarters of declining revenue for the tech giant, due to this year's iPhone cycle failing to outpace the record-shattering sales of fiscal 2018. Especially in light of that recent slump, investors will be watching the report closely.

Here are three key metrics to keep an eye on when Apple's fiscal Q3 results arrive.

Apple CEO Tim Cook kicks off Apple’s March 2019 event.

Apple CEO Tim Cook. Image source: Apple.

Total revenue

Apple's fiscal 2019 hasn't been looking good compared to the double-digit revenue and earnings-per-share growth it delivered in fiscal 2018. Revenue fell slightly in both Q1 and Q2.  In addition, EPS actually shrank in Q2.

Of course, shareholders are hoping these retreats are only temporary, and management is encouraging those hopes. The guidance range for fiscal Q3 revenue of $52.5 billion to $54.5 billion suggests the company may be returning to growth. If it hits the midpoint of that range -- $53.5 billion -- revenue will have increased slightly from the $53.3 billion it booked in fiscal Q3 2018. 

iPhone revenue

While Apple's revenue guidance represents management's expectations for all of its product lines, those figures also serve as a barometer for what it expects from the iPhone, which accounts for more than half of total revenue.

To this end, management did note in its fiscal Q2 earnings call that iPhone sales trends were improving, supporting the assumption that the outlook for total revenue to potentially return to growth reflects the expectation of reinvigorated sales of the device.

"For iPhone, while our worldwide revenue was down 17% from a year ago, declines were significantly smaller in the final weeks of the March quarter," said CEO Tim Cook. "Looking back at the past five months, November and December were the most challenging, so this is an encouraging trend. We like the direction we're headed with iPhone and our goal now is to pick up the pace."

While iPhone revenue will likely still be lower in fiscal Q3 than it was a year ago (other segments will likely help drive Apple's growth), expect the year-over-year decrease to be a single-digit percentage this time.

3. Services revenue

Apple's services have become increasingly important to its business. The services segment is now the tech giant's second-largest business, and its revenue is growing rapidly. Services revenue rose 16% year over year in fiscal Q2 to a new all-time record. Further, that growth is broad based; services revenue hit record highs in four of five of Apple's geographic segments during the quarter, management said on the earnings call.

Driving home how important the segment is, services revenue accounted for 20% of Apple's fiscal Q2 revenue, and a third of its gross profit dollars.

Given the segment's strong momentum and Apple's concerted efforts recently to grow this business, investors should look for services revenue to maintain that growth rate.

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