Anyone knows how to calculate/scale this feat?

[Godsatoshi23]

Five trump cards complete Cadence's greatest and most powerful magic.

"Hey, did you know? The total weight of Earth's atmosphere is about 5,000 trillion tons."

Like a stop-motion film, an ultra-compressed mass of air forms inside Leviathan's mouth.

"――Don't worry, it's about three orders of magnitude less than that."

The atmosphere equivalent to that of an entire nation is compressed to less than one cubic meter.

From here on, the actions are the same as what the legendary Ray Starling did.

"«Sigil of Yellow»"

――That is, the release of the compressed air.

Inside Leviathan's mouth――the largest fuel-air bomb on Earth exploded.

Basically It's a spell that compresses 5000 trillion tons of air into 1 cubic meter and then releases it.

For further information

The singular multi-layered ritual magic, "Sigil of Yellow."

A fuel-air bomb of unparalleled power in the history of magic, which compresses several trillion tons of gas to the extreme and releases it instantaneously, obliterating the surrounding area without a trace.

Cadence's ultimate combo, unleashed with all the cards gained during his days in <Infinite Dendrogram>.

At this moment, its power was unleashed on the surface.

The land became a devoid of a single tree or blade of grass as far as the eye could see.

The area, frozen over due to the rapid drop in temperature caused by the sudden decompression.

The sky, raging with turbulent air currents generated by the explosion.

A scene truly befitting the term "cataclysm."

The construction was flawless, and even with the process omitted, the magic activated without issue.

Any living being would die from such an explosion if it occurred within them.

Even a slime would be shattered to the point of being unable to preserve itself.

Leviathan was at the epicenter of such an explosion.

If Behemoth had stored it in the sigil just before, the Behemoth would die from the blast wave, having lost its status enhancements.

 

[Godsatoshi23]

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[Arkenis]

Basically It's a spell that compresses 5000 trillion tons of air into 1 cubic meter and then releases it.

Use this calculator. I think this should be what you're looking for. I tried it and got this in psi 761460000000000000000 of the cubic meter meaning thats how much pressure was needed to compress it.