Calc The day earth stood still (nardo)

Reasons to use our moon size
This is the same jutsu being used on pretty much the same situation that leaded to the creation of nardoverse's moon.
kakashi states it became just like their moon.
occam's razor should suffice with this much.

discovering the planet size
(http://imgur.com/R1Wef3i) when kaguya was sealed she became the core of a new moon for her planet
planet diameter 1919px
moon diameter 443px
moon radius 1736km
planet radius 7520.05417607 km
planet diameter 15040.1083521 km
getting planet's GBE
Now, i'll plug the planet diameter with earth's gravity on this PPC to get the planet mass
GBE=3GM^2/5r
G=6,67*10^-11
M= 8.311E+24 kg
R=7520054 m
GBE=3.6758914e+32 joules
kaguya's planet GBE

87.855913 zetatons

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Why Prime kaguya gets it
She has displayed full control over her dimensions.
After tooking out her goudama zetsu states she would " start a new dimension" (implying she created the other ones)
databook states she can destroy "worlds" with the goudama

reborns allmark said:

Kaguya's Expansive Truthseeker Orb (膨張求道玉, Bōchō Gudōdama) is listed as a Kekkei Mora ninjutsu. It says that she used the Divine Tree to absorb chakra from all of the shinobi and create a maximized (極大化) Truthseeker Orb. The equivalent (同じ物だが, same/identical/similar) black orbs that appear behind Naruto's back when using Six Paths Sage Mode can't be compared to its dimensions. Comprised of all five elements and yin-yang, it had the power to oblitrate the world and return it to nothing. Caption: Comprised of all chakra natures, a vast, expanding mass is filled to the brim. Created to reshape the world, it was a huge mass of chaos.

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If this is enough , we have a solid planet level feat for kaguya