Subfloor Calculator
Subfloor panels are typically 4×8 sheets of 3/4" OSB or plywood. Enter your room dimensions to get panel count with 10% waste, tubes of construction adhesive, and pounds of screws.
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Top Pick3/4" OSB Subfloor (4×8) — Home Depot~$34/sheet* Affiliate links — we may earn a commission at no cost to you.
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How to Use This Calculator
- 1Enter your measurements in the fields above. Use the units shown next to each field (ft, in, etc.).
- 2Click Calculate to get your material estimate instantly.
- 3Review the highlighted result — it shows the key quantity you need to order.
- 4Use Copy Results to save your estimate, or bookmark the URL — your inputs are encoded in the link.
Pro tip: Always add 10% to your material order to account for waste, cuts, and defects.
Frequently Asked Questions
How many sheets of subfloor do I need for a 20×15 room?
A 20×15 room is 300 sq ft. Each 4×8 panel covers 32 sq ft. With 10% waste, you need 300 × 1.1 / 32 = 10.3, so 11 panels.
Should I use OSB or plywood for subfloor?
OSB is the industry standard for subfloor — it's stronger than plywood of the same thickness, cheaper, and performs well when properly installed and kept dry. Use plywood in areas with high moisture exposure (crawl spaces, bathrooms) or when installing a tile floor that requires extra rigidity.