Stock index futures added to gains on Thursday after better-than-expected readings on weekly jobless claims and second-quarter gross domestic product.

Futures already were higher after Germany's lower house approved new powers for the euro zone's crisis fund.

S&P 500 futures rose 13.3 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration of the contract. Dow Jones industrial average futures gained 125 points, and Nasdaq 100 futures added 25 points.

(Reporting by Ryan Vlastelica; Editing by Kenneth Barry)