Warren Buffett likely took a $6 billion hit on just 4 stocks during Monday's painful sell-off

• Warren Buffett probably took a $6 billion hit on four stocks during Monday's sell-off.
• The investor's Apple, Bank of America, Coca-Cola, and American Express stakes fell in value.
• Buffett's Berkshire Hathaway has made over $150 billion in total gains on those positions.

Warren Buffett likely suffered a $6 billion blow to his stock portfolio on Monday, as four of his biggest holdings slumped in value during the painful market sell-off.

The investor's Berkshire Hathaway conglomerate counts Apple, Bank of America, American Express, and Coca-Cola among its largest positions. Those four stocks fell between 1% and 4% on Monday, wiping about $5.9 billion off the combined value of Buffett's stakes in those companies.

Berkshire boasted 887 million Apple shares at the last count. Assuming he hasn't touched that holding, it slid in value by $3.5 billion on Monday. The conglomerate also took a $1 billion hit on Bank of America, a $2.7 billion hit on Coca-Cola, and a $1.1 billion hit on American Express.

Buffett won't be too bothered, as he famously focuses on long-term performance, and has already made a fortune on those stocks. For example, Berkshire spent $36 billion to build an Apple stake worth $126 billion today, more than tripling its money on paper.

The investor's company also spent $1.3 billion for Coca-Cola stock worth $22 billion today - a roughly 17-fold gain. Moreover, its $25 billion stake in American Express has a cost base of $1.3 billion, and it spent about $15 billion to amass a Bank of America position worth $37 billion today.

Overall, Buffett's total unrealized gains on those four stocks exceed $150 billion - more than the market capitalizations of Starbucks ($136 billion), IBM ($123 billion), or Goldman Sachs ($120 billion).

Buffett concentrates his money in a few key investments instead of spreading it across hundreds of them, boosting his returns when his bets pay off, but also exposing him to sharper declines. Apple has made up 45% of the total value of Berkshire's stock portfolio in recent weeks, and the conglomerate's top five holdings have accounted for 75%.