Stock futures added gains on Friday after Microsoft Corp reported first-quarter results, while investors awaited existing home sales data later in the morning.

S&P 500 futures rose 3.50 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures added 12 points, and Nasdaq futures gained 12.50 points.

(Reporting by Leah Schnurr; Editing by Theodore d'Afflisio)