Amazon's value surpasses Wal-Mart after surprise 2Q profit, but still not in top 10 of S&P 500

Amazon surpassed the world's largest retailer, Wal-Mart Stores Inc., in market value Friday, on the back of a strong earnings report. Amazon shares closed up nearly 10 percent, giving the Seattle company a market value of $247.77 billion, versus $230.53 billion for Wal-Mart.

A company's market value is calculated by multiplying the number of shares of stock it has in circulation by the current price of one share.

Here's the list of the top 15 companies in the benchmark S&P 500 index, followed by their market value:

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Source: FactSet