User blog comment:IamJakuhoRaikoben/Chapter 371: Tartarus Arc: Part 2 - Song of the Heavenly Dragon, Review./@comment-4449950-20140216015651/@comment-7418318-20140217183857

That's not even necessarily true in reality, much less a fantasy setting.

For example a Frag Grenade has a higher radius in which it causes damage than one purely out of high explosives. So the HE does more damage, while the FRAG has a bigger radius. Then there are also shaped charges, which concentrate the majority of the explosive force in a tighter field.

And since we're talking about MAGIC here, Hiro Mashima could combine explosive force and radius in pretty much any way he wants. He could make an explosion shaped like the letter X that completely vaporizes anything within and has no collateral damage what-so-ever if he felt like it.

Now if you said that it couldn't have been 500 times Jupiter because there was still rubble left, even though such a massive explosive force would turn everything in it's radius to dust, that I could accept, but the radius by itself isn't much of an argument about the force of the explosion.