I wasn't happy with any of the commercially available or printable spell templates for 5e spells and have been needing to brush up on my CAD skills. This is a work in progress of various spell templates, starting with the easiest shapes and I will be adding the more complex shapes (cones) once I get my basic design parameters dialed in.

These are made for a 1" square grid, while you can just rescale for 1.25" or 1.5" grids I do plan on making versions for those sizes so it doesn't make them too thick.

UPDATE-01 I have added cones. There is a 15"+30" version, a 30"-only version, a 60" addon to the 30", along with a 30" + 60" version that I'm pretty sure most people (including myself) can't fit on their bed.

UPDATE-02 It was brought to my attention that the source of all spells in 5e should always be the corner of grid squares and not the center of a square. I'll be adding a new circular template that has a simple crosshair design so you can target it to the corner of a square, but I'm going to also leave the square targeting version since it seems to be how many people prefer to target fireballs.