Deck Post Calculator
Rectangular deck outline with posts on outer grid.
Step 1: Units
Step 2
Enter project measurements
Use decimals if needed (e.g. 3.5).
How to use this calculator
Overall length and width of deck outside of posts; spacing along each edge.
What the math is doing
Approximate posts = 2×(ceil(L/s)+ceil(W/s)) minus double-counted corners.
Frequently asked questions
Mid-span posts?
Add for long beams.
Corner sharing?
This model double-counts corners lightly—round up.
Rail posts?
May coincide with structural posts.
Stairs?
Add newel posts separately.