A quick link here for online gear ratio calculators, for finding or comparing gear ratios, sizes, or gear inches. Especially helpful when fine tuning spin, or trying to match spin between different sized bikes. I always had trouble remembering where these handy tools lived online, so I figured I would create a post and put one here permanently.
For reference, the standard 20″ BMX gearing is 44T on the front, 16T on the rear, 44/16. That gives you 55 gear inches. 41/15 gives you 54.7 gear inches, which is very close. So you can see how you can change sizes front to back and still achieve the same basic gear inch size, giving you the same resistance at the pedals.
For 24″ cruisers, factory Redline runs 41/18, for 54.7 gear inches.
On my 26″ Ti P, I run 32/14, for 59.4 gear inches, a bit taller for a bigger wheeled bike.
Keep in mind that tire size/volume and crank length can affect the actual ratio and feel, apples to apples…
UBI Gear Chart