How to calculate this feat ?

[Franstel]

The feat:

Then it morphed into a spiral of orange fire and whirled toward the nearest of the witches. She disintegrated in an explosion of flesh and blood. Tiny fragments of bone fell from the air like hail, but rather than melting on contact with the rock, they hissed like hot cinders falling into water.

 

[AlexSamDen]

The feat:

What do you even want to calc from this? Rn I see only that the temperature was so high that it started melting the rock on contact. For that you need the heat energy required to melt through the rock in like 0.5-1 seconds

 

[Franstel]

What do you even want to calc from this? Rn I see only that the temperature was so high that it started melting the rock on contact. For that you need the heat energy required to melt through the rock in like 0.5-1 seconds

The violent fragmentation of a human being

 

[AlexSamDen]

The violent fragmentation of a human being

That is hard to go off. It can be attributed to her expanding beyond limits due to temperature, can be deconstruction or some special properties. It's hard to tell due to the fact that it seems like a hax and not direct physical attack

 

[Franstel]

More context for the feat:

For a moment Kratch was visible as a giant catlike beast—a fearsome distortion of the ginger tomcat sometimes glimpsed in the kitchen at Chipenden. Then it morphed into a spiral...

Kratch shapeshift himself into a vortex of energy before ramming into the witch killing her.
It's not the only time he did it, a few more examples:

Then the boggart attacked. As it sprang toward the steps, the witches turned and fled, shrieking in their terror. Their frantic retreat was uncoordinated; the ones nearest to the open door did not turn fast enough. Witch collided with witch, and some fell onto the rocks below.

I saw the boggart swipe one with its paw, then bite her head from her body. But it was already losing definition; the monstrous cat was changing into a vortex of orange energy that spiraled upward into the mass of witches, filling the air with a mist of blood and tiny fragments of bone.

It took less than three seconds for the boggart to kill all those on the steps and enter the tower through the open door. Then there was an eerie silence—for there were no witches left to scream. There were no bodies to be seen, either. A tide of blood was flowing down the steps, carrying with it dozens of pairs of pointy shoes.

And

It sent the first two or three flying with swipes from its gigantic paws. Another was seized in its jaws and bitten in half. Then it seemed to dissolve and became a great spinning tornado of fire and energy that smashed into the warriors; the air was filled with blood and fragments of bone, and the screams and wails of its victims.

The central mass of the attackers was destroyed in seconds; then the vortex of fire began to pursue individual warriors as they fled back towards the trees. Not one survived.

 

[AlexSamDen]

More context for the feat:

Kratch shapeshift himself into a vortex of energy before ramming into the witch killing her.
It's not the only time he did it, a few more examples:

And

Still doesn't help, even worse, with "energy" being used alongside fire it's even less quantifiable as AP and leans more into hax department, such as Limited Explosion Manipulation or Deconstruction. The best case you can have from here is the bite force and the heat produced

 

[Franstel]

OK
Thanks

 

[Tyrone_Dawson]

The feat:

If it were an explosion, it could kind of be calculated.

The human body is made of approximately 60% water, or about 42 kg for an average 70 kg person. 1 kg of water, when turned into water at atmospheric pressure, occupies about 1.6 cubic meters.

The conversion of 42 kg of water into steam would generate 60 cubic meters of steam.

An estimate for the violent fragmentation of the human body is approximately 7.533 Joules per cubic centimeter.

So if it were a fire explosion, it would take approximately 200 megajoules of energy.

And if the vortex energy were a type of mechanical energy, it would require 4.83 megajoules of energy.

Sorry, I can't help more since it's a combination of both; it's not really calculable.