Native Planting Spacing Calculator
Sometimes it gets confusing trying to figure out the number of native plant plugs for a project if we want to use 9″ centers or the number of native shrubs if spacing is every 4′.

Viola! Attached is a simple EXCEL file, with no macros, that will easily calculate how many plants you need; all you do is enter the square footage of your project. The green dark bars are common spacing for herbaceous and woody species, respectively. The little red triangles are notes; hover your mouse over them to read the note.
ArcheWild – Plant spacing calculator
Good luck.