Power tools seller W.W. Grainger Inc. said Thursday that its board approved spending $3 billion to buy back its own stock over the next three years.

The company expects to buy back $1.4 billion in stock this year and $800 million in 2016 and another $800 million im 2017. Grainger will pay for the buybacks with a combination of cash and new debt. It will know the exact number of shares it bought at the end of 2017.

Buying back stock can help support the company’s share price and earnings per share.

Grainger said it expects the buyback to add between 8 cents per share and 12 cents per share to its 2015 earnings.

Also Thursday, the Lake Forest-based company also reported first-quarter earnings and revenue that missed Wall Street expectations, according to analysts surveyed by Zacks Investment Research.

Shares of Grainger rose $7.93, or 3.3 percent, to $249.89 in morning trading Thursday. Its shares are down slightly in the past 12 months.