What can the Fed buy with its behemoth balance sheet?

Officials at the Federal Reserve want to start winding down the massive $4.5 trillion balance sheet the central bank has built up. The news came Wednesday when minutes from the Federal Open Markets Committee's March meeting were released.

During that meeting, the members of the committee voted to raise the federal funds rate a quarter of a point, the third such hike since the financial crisis. The Fed built up the behemoth balance sheet over the past decade through several rounds of quantitative easing, buying up bonds and mortgage-backed securities and has been discussing how to wind it down.

When you're talking about numbers that high, things get out of perspective. We thought we'd help out and show you what $4.5 trillion could buy.

For one thing, the Fed could buy up most of the companies in the S&P 500. A full 315 individual companies, when counting from the bottom of the list by market capitalization. That includes well-known names like Viacom, Clorox and Expedia.

On the other end, the Fed's spending spree could purchase the top 10 companies: everything from Apple to Wells Fargo. That includes a lot of big outfits like Amazon, Alphabet and Exxon Mobil.

But the Fed maybe should have wound down its balance sheet years ago: A previous CNBC analysis showed that in December 2015, it could have afforded the 14 biggest companies in the index.

"Provided that the economy continued to perform about as expected, most participants anticipated that gradual increases in the federal funds rate would continue and judged that a change to the committee's reinvestment policy would likely be appropriate later this year," the March minutes said.

The Fed's balance sheet is around 24 percent of U.S. GDP, which is far above the historical average of around 6 percent. But other industrialized nations have asset-to-GDP ratios that are much higher. The Fed's total assets have plateaued in recent years while those of other central banks like Japan and the European Union have continued to rise.

In terms of sales, the Fed's assets are worth about nine times the annual sales of Wal-Mart, which led the S&P 500 last year. It's equal to the total sales of the top 33 companies, or the bottom 441 on that list.