If I have a 16t gear and a 36t gear does that mean I will have a 1:2.25/2.25:1 ratio even though both are using 2 degree GT2 belt? A simple question I am sure. edit: What is throwing me is the GT2 belt part as I am used to chains, rope, spur gears and if this follows the same rules as other stuff then my ratio is right but if it follows the size of one vs the other then I would be wrong. Another thing is what would the steps be for something like that?

Wheel, gear, pulley... They all work on the same principle. It's all a ratio of drive diameters. For pulleys, it's just easier to use the tooth count to calculate the ratio. Also, pulleys and timing belts are defined by their pitch, not degrees. GT2 defines the tooth profile, but they come in 2mm and 3mm pitch (distance between teeth). 2mm is the common size, and the one commonly sold on the OB store. 3mm is also known at GT3, and while available on the OB store, there aren't as many options. GT3 was what was used on the C-Beam belt reduction kit. As for the steps, just multiply the steps required without the reduction/increase by the ratio. If you have say 100 steps per millimeter before adding the belt reduction/increase, then the final steps for the 1:2.25 ratio would be 225 (100 * (2.25/1) = 225). For the 2.25:1 ratio, the steps would be 44.4444 (100 * (1/2.25) = 44.4444).

The number after the GT is the belt product series. GT2 and 3 belts each come in a number of different pitches and widths. For example, minimum pitch available on the GT3 series is 5mm and the next is 8mm, then 15. The tooth profiles are the same for each making them backwards compatible with GT2 pulleys. The GT3 belts are thicker giving them higher ratings. The Powergrip GT series originated with Gates and their site has all kinds of technical and design info for these belts and pulleys. That said, chances are you have a 5mm pitch belt. 16 teeth in a full rotation x 5mm per tooth is 80mm of belt travel per rotation. If 200 full steps per rotation gives you 80mm. 80mm/200steps is .4mm per step. .4mm per step/2.25 ratio = .177777 per step (round in software as you please). At work. Someone check my math Joe.

Easy to do. @Mark Carew I just noticed this info in the parts store for belts and pulleys is incorrect.

Thanks everyone and I thought the 2 meant 2mm pitch and the 3 3mm pitch so interesting. I just wish I could find a GT2 12t 5mm bore gear but I couldn't. I can find it in a 4mm and a 6mm bore but for some odd reason I couldn't with a 5mm bore.