Fron NASA's Solar Dynamics Observ. The flare was an X class measured at X 2.1.
We should hear more from the NASA solar physics folks tomorrow on how much of this was directed toward Earth, and what effects it will have.
X-class flares are the most powerful. Less powerful flares (like M class) are rated on a scale of 1-9 but there is no top end of the X-class flares.