What is the weighted average of shares outstanding?

The weighted average of shares outstanding is used to determine a public company's earnings per share. Private companies are not required to report earnings per share, so they do not need to calculate this number. The weighted average incorporates the beginning number of shares outstanding, plus additional shares that were sold or otherwise issued during the period, minus any shares that were bought back during the period.

For example, a business has 1,000,000 shares outstanding at the beginning of the calendar year. It sells an additional 100,000 shares at the beginning of June, and buys back 300,000 shares at the beginning of October. The calculation of its weighted average shares outstanding for the full year is as follows:

+ 1,000,000 shares outstanding in January

+ 1,000,000 shares outstanding in February

+ 1,000,000 shares outstanding in March

 + 1,000,000 shares outstanding in April

 + 1,000,000 shares outstanding in May

 + 1,100,000 shares outstanding in June

 + 1,100,000 shares outstanding in July

 + 1,100,000 shares outstanding in August

 + 1,100,000 shares outstanding in September

   +  800,000 shares outstanding in October

   +  800,000 shares outstanding in November

 + 800,000 shares outstanding in December

=11,800,000 shares in total, divided by 12 months

 = 983,333 weighted average of shares outstanding

In addition, the company earned $1,600,000 of net income during the year. When divided by the 983,333 weighted average of shares outstanding, this results in $1.63 earnings per share for the year.