First of all let me tell you that Kubo personally supervise each movie and it was written by him. There's been moments in the manga when certain things from the movies are addressed in it. We have proof that Soul Society is planet size in two different non-canon movies (which are debatable) and once in the manga which is above this comment.
1-
According to the Bleach Movie "Fade to Black" Seireitei is 400 spirit miles for it's diameter
Kubo over seed the production of this movie by the way http://bleachness.livejournal.com/219899.html
1 spirit mile=2.4 spirit miles
400x2.4=960 miles
This is the diameter of soul society
Now that makes Gremmy's meteor which is close to the size of seireitei that large. Then you have to factor in density and the fact it was mving at hypersonic speeds given it's flames.
If a 10km meteor that wiped out the dinosaurs was country level then something close to 960km is easily continental-multi continental.
Remember, In 10 days, if you walk for 16 hours a day you can walk for 160 hours.
160 hours x 5 km/h = 800 km
Yep. Seireitei is easily over 800 km in diameter (which is 200 spirit miles according to the canon movie) So a 200-400 km wide meteor will have a multi continent level impact considering a 10km meteor can lifewipe the dinosaurs and create a country sized crater.
2-Another cal for the seireitei,
Back in the Soul Society, Kubo had Yoruichi state that it would take ten days to walk from one gate of the Shakonmaku to the next one. The Four Gates are located at the cardinal directions, so it takes ten days (according to Yoruichi) to walk around a quarter of the Seireitei's circumference. Because the calcs for size that use pixel scaling are the ones generally accepted, people mainly considered Yoruichi's statement to be nonsensical at best.
However, there is an image where a size comparison between the Rukongai and the Seireitei can be made.
Namely, from a panel on this page:
http://www.**********.com/94-525-19/...hapter-71.html
Also supporting Yoruichi's statement is the fact that it was made i
n regards to the plot. They would have wasted time trying to walk to the other gates (10 days), which necessitated the used of the Kakaku Cannon. The fact the statement was used in relation to the plot validates it from an in-universe standpoint.
Here's a link to the page in question:
http://www.**********.com/94-530-15/...hapter-76.html
Here is the image which I used to scale the Seireitei's diameter to the Rukongai area -
[1]
Rukongai width - 93 pixels
Seireitei diameter - 133 pixels
Roughly, this means that the Seireitei's diameter is 1.43 times that of the distance the Rukongai stretches in one direction.
Sables' old calc for
Yamamoto blowing up the Soul Society establishes what the distance would be (in this case radius) if you lined up 80 Japanese districts together.
There is a high-end and a low end for the size of the Rukongai, so I'll use both:
Sables' Rukongai = 1504 kilometres
Fluttershy's Rukongai = 336.83 kilometresSo a high-end and low-end distance can be attained by multiplying them by the ratio of size between the Rukongai and Seireitei. High-end Seireitei size (Sables) =
2150.72 kilometres
Low-end Seireitei size (Fluttershy) =
481.67 kilometres
NOTE: After looking around a bit to find out how far the average person can walk in a single day (multiply that by 10 to get the distance from one gate to another around the Shakonmaku), it was 24 miles for walking an average 3 miles per hours for eight hours.
If that were taken into consideration, you'd get a circumference of the Seireitei of 960 miles, and a radius of 245.89 kilometres, which makes the diameter around 491 kilometres.
As a result, that means the "low-end" is actually the one closest to reality in this situation.We have already seen the cycle of day and night. Also we have seen the vast land and mountains outside of the sereitei which are shown in the manga. Not to mention that Aizen and Ichigom fought in Soul Society outside of Karakura Town.
Edit: Let me add this, Assuming the walking speed of the average human is 3.1 mph (source: wikipedia), and it takes ten days to walk from gate to gate, then, assuming the walk is continuous for the duration, the gates are approximately 744 miles apart. As far as the actual area of Seiretei, it would depend on its shape and whether the walk is along the perimeter of the wall, or the shortest distance between each gate inside of Seiretei (a diamond pattern in this case).
For simplicity's sake, I'll assume the walk is along the outside perimeter, and that Seiretei is a rectangle, the dimensions of which would be 744 miles by 744 miles, given that the four gates are equidistant and located at the center of each side. The square mileage then would be 553,536 sq miles, or over twice the size of Texas.