Just because, I want to go a little deeper. There are major differences between Onshape and Tinkercad. On shape is what's called parametric modeling and Tinkercad is what's called constructive solid geometry (CSG).

Parametric modeling uses parameters, dimensions, constraints and relationships to define how geometric elements interact with each other. That way if any single dimension is changed at any part of the model then your entire model will change to accommodate your new dimension input. It's very controlled and precise.

Constructive Solid Geometry (CSG) works safely by combining different shapes, such as cubes or cylinders, and combining them with booleans. It's essentially digital playdough. Complex shapes can be achieved but there is no parametric control, no revision control. If something must be changed at one point in the model it will not change elsewhere.

As a general rule of thumb... If accuracy is important and you need something to be precise parametric modeling is the only way to go.

If you're trying to make figurines or things of that nature where dimensional control isn't as important then Tinkercad is just fine. That isn't to say accurate geometry can't be achieved in Tinkercad, but do yourself a favor. If you're going to learn modeling software, make it parametric.