There is 7 common sizes: Small, Human, Monstrous, Towering, Gargantuan, Titanic, and Astronomical
The way to represent Size is through a scale of nine size aspects: Mirco, Tiny, Small, Human, Monstrous, Towering, Gargantuan, Titanic, and Astronomical. The Size aspect could be both invoked a compelled for a variety of reasons. Larger attackers could invoke it to hit harder or shrug off damage, while smaller defenders could invoke to sneak away or be more swift.
Targets that find themselves inside of the same size on the ladder are not able to invoke the aspect for any numerical or narrative benefit.
It is nearly impossible for a normal human-sized target to affect above a Towering Sized Creature. However if it is narratively appropriate you may allow characters to create advantages that will allow them to change their Size Scale.
For example during the 4th Shinobi Great War, the Hokages managed to create large companies of shinobi that were able to synergize together and use the same jutsu as the company leaders. Due to the mass power of the Kages, they managed to pull their resources together and jump the size ladder to Gargantuan thus able to target the Astronomical Ten Tails in collaborated actions.
Human sized creatures are not able to affect a target larger than “Towering ”size. By the same token very large creatures are unable to directly attack human sized creatures, though many people die due to collateral damage by attacking the zones or sector. Thus without proper narrative aspects a target three Sizes larger than you ignores any attempt to directly affect it. The reverse is also true: an attacker three Sizes larger cannot directly target you but may target the zone or sector that you are currently in. Also check out Breaking Things.
Micro: Germs, Chakra Signatures
Tiny: Infants, Mice, Rabbits, Birds.
Small: Small Children under 7, Normal Dogs, Cats, Pigs ect. Low Tier Summons.
Human: Normal Human Beings no matter the size.
Monstrous: Grizzly Bears, Elephants ect.
Towering: Mid Tiered Summons and Oni
Gargantuan: Most Epic Tiered Summons , Dragons.
Titanic: Tailed Beast
Astronomical: Ten Tails, Ancient Oni and Elder Dragons
In Naruto Fate, Zones have a baseline size, which would be represented by a average sized room within a house. Zones may increase or decrease in size based on the need of the GM and the players. When structures get to a certain size they no longer operate as Zones but instead turn into Sectors. Things of Gargantuan and Larger no longer operate on Zones and instead operate on sectors which are the same as zones but cover a lot more distance. Example: A small village with 3000 people might be two sectors but could easily be 12+ zones worth of space.