Method 1[]
Scaling Image 1 - Size of the Biju Bomb[]
Madara's Height = 12 px = 1.79 m
Biju Bomb = 90 px = 13.425 m
By comparing Madara (inside of his Susano'o) to the Biju Bomb, we can get an approximation of its size.
Scaling Image 2 - Size of the Rashomen[]
Biju Bomb = 77 px = 13.425 m
Rashomen = 440 px = 76.7142857143 m
This gets us the height of the Rashomen summoned by Hashirama, which is important for the next step.
Though we cannot see the exact bottom of the Rashomen, we know it cannot be much further than what is shown judging by every time we have seen the Rashomen in the past such as here and here.
Scaling Image 3 - Size of the Biju Bomb Explosion[]
Rashomen Height = 32 px = 76.7142857143 m
Close Wake = 160 px = 383.571428572 m
By getting a rough estimate of the size of the wake of the Biju Bomb on the near shore, we can make an estimate of the size of the explosion by looking at the wake on the far shore.
Distant Wake = 8 px = 383.571428572 m
Biju Bomb Diameter = 70 px = 3356.25 m
Biju Bomb Height = 30 px = 1438.39285715 m
This gets us an approximate size of the distant explosion.
Volume & Destruction[]
Unfortunately we never get a good glimpse of the crater left behind by this explosion, but I'll calculate this as a half-ellipsoid to get the volume of destruction:
V = 2/3 * π * a * b^2
Volume = 2/3 * π * 1438.39285715 * 1678.125 * 1678.125 = 8,483,689,129.55 m^3
Volume = 8,483,689,129.55 m^3 = 8,483,689,129,550,001 cm^3
Destruction (Vaporization) = 8,483,689,129,550,001 cm^3 * 25700 = 2.1803081e+20 joules
2.1803081e+20 joules = 218,030,810,000,000,000,808 joules = 52.11 Gigatons
Method Two[]
Using the first image from the first method to get the size of the Biju Bomb.
Scaling Image 2 - Full Biju Bomb Diameter[]
Biju Bomb = 77 px = 13.425 m
Biju Bomb (with Sword) Diameter = 371 px = 64.6840909091 m
The reason why I'm using a separate image to get the full diameter of the Biju Bomb (with the sword taken into account) is because the sword on the first panel is at an angle towards the viewer and isn't suitable for getting the full length of it.
Scaling Image 3 - Shore Width[]
Biju Bomb Diameter = 12 px = 64.6840909091 m
Shore Width = 92 px = 495.911363636 m
For the ease of visualization, I've filled in the missing pieces of the circumference. Here is what the page looks like without pixelscaling.
By comparing the full width of the Biju Bomb (with sword included) to the shore, we can use that width in calculating the size on the far side of the body of water.
As seen in the anime, the circle around the dot that is travelling across the water is the circle made by the blade spinning around at high speed. A screenshot of the specific moment can be found here.
This scaling for the size of the Biju Bomb (sword included) is also consistent with the size of the Rashomen knocked over on the land.
Scaling Image 4 - Biju Bomb Explosion[]
Close Wake = 160 px = 457.764335664 m
By getting a rough estimate of the size of the wake of the Biju Bomb on the near shore, we can make an estimate of the size of the explosion by looking at the wake on the far shore.
Distant Wake = 8 px = 495.911363636 m
Biju Bomb Diameter = 70 px = 4339.22443181 m
Biju Bomb Height = 30 px = 1859.66761363 m
Volume & Destruction[]
Volume = 2/3 * π * 1859.66761363 * 2169.61221591 * 2169.61221591 = 18334040079.7 m^3 = 1.83340400797e+16 cm^3
Destruction (Vaporization) = 1.83340400797e+16 * 25700 = 4.7118483e+20 joules
4.7118483e+20 joules = 471,184,830,000,000,000,192 joules = 112.616 Gigatons
Method 3[]
Scaling Image 1 - Biju Bomb[]
Madara Uchiha Height = 12 px = 1.79 m
Biju Bomb Height = 90 px = 13.425 m
Scaling Image 2 - Full Diameter[]
Biju Bomb Height = 77 px = 13.425 m
Full Diameter = 371 px = 64.6840909091 m
Scaling Image 3 - Coast Width[]
Full Diameter = 17 px = 64.6840909091 m
Coast Width = 68 px = 258.736363636 m
Scaling Image 4 - Explosion[]
Coast Width = 106 px = 258.736363636 m
Near Wake = 160 px = 390.545454545 m
Far Wake = 8 px = 390.545454545 m
Explosion Width = 70 px = 3417.27272727 m
Explosion Height = 30 px = 1464.54545454 m
Volume & Destruction[]
Volume = 2/3 * pi * 1464.54545454 * 1708.63636363 * 1708.63636363 = 8954900376.57 m^3 = 8954900376570000 cm^3
8954900376570000 * 25700 = 2.3014094e+20 j = 55.005 Gigatons (Island level+)
Results[]
Prime Kurama Attack Potency (Method 1) = 52.11 Gigatons (Island level)
Prime Kurama Attack Potency (Method 2) = 112.616 Gigatons (Large Island level)
Prime Kurama Attack Potency (Method 3) = 55.005 Gigatons (Island level+)