The world needs a new source of energy, an unspillable source.

How much Hydrogen is needed to react in a Hydrogen fuel cell?

So, my question is if anyone knows or can point me to a link is, how much compressed hydrogen is needed to react with a fuel cell to produce enough electrical power to at least equal the amount of drivable distance as a modern gasoline powered car? I can understand that no one may know this as a result of industry secrets and what not, but ill take anything.