Use this floor sheathing calculator to estimate how many OSB, plywood, or tongue-and-groove subfloor panels you need for a floor, room, addition, decked platform, garage area, or repair section.
This is a material planning calculator, not a structural floor design calculator. It does not choose panel thickness, span rating, joist spacing, fastening schedule, adhesive, blocking, deflection limits, moisture exposure rating, or code compliance.
Estimate your floor sheathing sheets
How this estimate works
The calculator multiplies floor length by floor width and the number of similar sections, or uses a known floor square footage. It subtracts large openings, adds waste, divides by panel coverage, and adds optional extra sheets for layout cuts or repair uncertainty.
When this floor sheathing calculator is useful
- Estimating OSB or plywood sheets for floor sheathing or subfloor panels
- Planning a room, addition, garage, shed, platform, or repair area
- Checking a material list before ordering panels
- Estimating repair panels when water damage, soft subfloor, or old underlayment is being removed
What this calculator does not decide
This calculator does not choose panel thickness, joist spacing, panel span rating, subfloor adhesive, fastening schedule, blocking, deflection performance, squeak control, or code compliance. Those depend on the floor framing, local code, manufacturer instructions, and sometimes engineering.
Do not buy only the mathematical minimum
The base sheet count assumes every offcut is reusable. Real floor sheathing work has seams, staggered joints, stair openings, plumbing cuts, damaged edges, repair surprises, and panel orientation requirements. A waste allowance is safer than buying the exact square-foot count.