John Shinal

Special for USA TODAY

Investors should get ready to hear a lot more about the negative impact of foreign exchange rates on the financial results of large U.S. tech companies.

That's because the strengthening of the U.S. dollar, which began a year ago on fears of economic turmoil in China, is about to accelerate due to the decision by U.K. voters to leave the European Union.

If recent history is any guide, Brexit-driven currency moves will likely cost tech giants Apple, Microsoft, Facebook, Oracle and Google-parent Alphabet hundreds of millions in quarterly revenue.

All of these firms have large overseas operations and late last year, as the dollar moved higher, they began sharing a new financial metric with investors.

While the exact wording has differed among the firms, it's essentially a measure of revenue excluding the impact of foreign currency swings.

And that impact is considerable, based on a look through their latest financial releases, SEC documents and earnings call transcripts.

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Apple took the largest hit, as Apple (AAPL) CEO Tim Cook explained near the start of his remarks on the company's April earnings call for the first three months of the year:

"We saw continued currency weakness in the vast majority of our international markets. In constant currency, our revenue declined by 9% from last year, 400 basis points less than the reported decline of 13%."

Doing the math yields a currency impact of $2.3 billion.

Microsoft (MSFT) also got slammed by currency moves in the first three months of the year , reporting a "constant currency impact" to revenue of $838 million in a table included in its earnings release.

The impact on its net income was $443 million, or 6 cents a share, showing the impact on investors.

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As the company put it in its 10-Q filing with the SEC: "Strength of the U.S. dollar...negatively impacted reported revenue and reduced reported expenses from our international operations."

The statement is a reminder that currency moves are not all bad.

Along with crimping revenue, they can also cut overseas expenses, because employees and contractors in foreign locations are usually paid in local currencies.

But the overall impact is sharply negative, and looks set to worsen in the wake of Brexit, especially for those firms with large operations in the U.K. All the major tech stocks were down 2%-4% Friday.

Google parent Alphabet (GOOGL) said its first quarter currency effects were a whopping $593 million. That cut the company's top-line growth to 17% from 23% year-over-year.

Of the total currency hit, the weakening of the British pound lowered Alphabet revenue by $87 million, the company reported.

On Friday, the pound dropped as much as 10% to a three-decade low, suggesting Alphabet's Brexit-driven currency impact could be much larger in coming quarters.

At Facebook (FB), the first-quarter currency impact to total revenue was $202 million, cutting potential year-over-year growth by six percentage points, to 52% from 58% , according to company filings.

At Oracle (ORCL), meanwhile, currency moves impacted both quarterly revenue for the three months ended May 31 and full-year profit for the just-ended fiscal year, as these paragraphs from its earnings release last week make clear:

"Without the impact of the U.S. dollar strengthening compared to foreign currencies, Oracle’s reported GAAP Earnings Per Share would have been 2 cents higher and non-GAAP Earnings Per Share would have been 1 cent higher" in its fiscal fourth quarter.

"For fiscal 2016, total revenues were $37.0 billion, down 3% in U.S. dollars and up 2% in constant currency."

In a related trend, both Apple and Microsoft helped manage their currency risks via foreign-exchange contracts that totaled at least $5 billion during the first calendar quarter.

That staggering figure suggests hedging against currency volatility may soon become one of the most important skills that chief financial officers of tech companies will need to serve their shareholders.

With the Brexit vote is seen driving the dollar higher against the euro and the pound this year, look for the currency impact on U.S. tech firms to grow.

John Shinal has covered tech and financial markets for more than 15 years at Bloomberg, BusinessWeek,The San Francisco Chronicle, Dow Jones MarketWatch, Wall Street Journal Digital Network and others. Follow him on Twitter: @johnshinal.