Free tool
Build a target where every small square is one click on your optic. Count squares, turn that many clicks. Pistol or rifle, any caliber. Works at your real zero distance, or as an offset target when your range is shorter than the zero you want, like a 100-yard rifle zero shot at 15 to 25 yards.
Every square is sized to your optic's clicks, so scaling the page breaks the math. The sheet has a 5-inch ruler bar; measure it before you trust the grid.
If you shoot closer than your zero distance, the bullet hasn't risen to your line of sight yet, so a correct zero prints low at the near distance. This tool marks where your group should land. Two things to know before you rely on it:
The mark comes from a standard trajectory calculation (G1 drag, standard air) run in your browser for the numbers above. Typical loads are filled in as a starting point; your ammo and barrel will differ.
Offset targets are a workaround for short ranges, not a replacement for confirming your zero at the distance you chose. The course covers the whole process, including the confirmation step.