This tool was added as a fun way for visitors to get a quick visual size comparison of their favorite Zoids for team balancing, fics, etc. That being said, the tool isn't perfect. Far from it. There are a lot of Zoids missing. Some Zoids are inevitably not going to scale properly, as some official stats straight up don't match other variants, requiring some fudging of sizes. For example, if we measure Energy Liger at the top of its blade, it ends up way smaller than other Ligers, when it's actually larger. Please use this page as a loose reference only. It's provided strictly for fun and not as a concrete reference.
So, how are the sizes actually calculated then?
I've measured most Zoids at their highest point, including equipment. For example, Liger Zero (8.3 meters tall) vs Liger Zero Panzer (9.7 meters tall). As stated, these numbers sometimes don't math no matter how you adjust weapons or position. I'm 99% certain TT didn't intend for Shield Liger DCS to use a smaller Shield Liger, for example. Some Zoids may appear higher on the meter than their official stats if weapons are out (I try to estimate based on weapons stowed, with some exceptions.)
Wherever possible, I rotate the images and slice off the bottom to make sure that the 'standing point' of each Zoid is roughly the same. Sinker, for example, is cropped so that it begins at the actual bottom section of the Zoid (the large cylinders in this case, not the fin sticking out of the image.) Some Zoid widths are also squished to make them fit on the page, but the heights should still be in the ball park. Non-scale Zoids, like Serpent, are compared to 1/72 scale models if they have a kit (even if it's non-scale.)
WAIT!!! Why is Death Saurer so small???
This page uses almost exclusively battle story / box stats, unless said stats are only available through other sources. The anime radically sizes up some Zoids. No anime-specific sizes are included here. I'm as offended about Death Stinger as you are, but yes, canonically, it's smaller than Blade Liger in every dimension.