UPDATE 2-Cloud storage firm Box's shares fall after company's conservative Q3 forecast

forecast@ (Adds CEO quote, details; updates shares)

Aug 28 (Reuters) - Box Inc on Tuesday forecast third-quarter revenue that was below analysts' estimates and a bigger-than-expected adjusted quarterly loss, sending its shares down 3 percent in extended trading.

The cloud storage provider's second-quarter revenue topped Wall Street estimates despite a rise in costs that the company has been incurring to attract new customers.

For the third quarter, Box sees revenue between $154 million and $155 million while analysts were expecting $155 million, according to Thomson Reuters I/B/E/S.

The company expects an adjusted loss of 7 cents to 8 cents per share for the third quarter which analysts' estimate a loss of 6 cents per share.

"We expect to have a non-GAAP profitability quarter in financial year 2019," Chief Executive Officer Aaron Levie, told Reuters, adding that Box is currently in the best position it has ever been competitively.

For the full-year 2019, Box forecast an adjusted loss of between 16 cents and 18 cents per share, while analysts, on average, were expecting a loss of 18 cents per share.

Box also raised the lower end of its full-year 2019 revenue forecast to $606 million from $603 million, keeping the higher end at $608 million.

Box, which competes with Dropbox Inc, Microsoft Corp's OneDrive and Google's Drive, signed more than 87,000 paying customers in the quarter, up from 85,000 in the previous quarter.

The company said its net loss narrowed to $38.1 million, or 27 cents per share, in the second-quarter ended July 31 from $39.3 million, or 30 cents per share, a year earlier.

Excluding items, Box reported a loss of 5 cents per share, while analysts were expecting a loss of 6 cents per share.

Revenue rose 20.6 percent to $148.2 million, above estimates of $146.5 million.

Box's shares have risen around 23 percent this year. (Reporting by Akanksha Rana in Bengaluru; Editing by Shailesh Kuber)