Plywood and OSB come in 4 × 8 ft sheets (1220 × 2440 mm) in most markets, with longer and metric sizes available. Count sheets by area for subfloors, sheathing and roof decking, then add waste for cuts, especially around openings and on hip roofs.
How to use the Plywood Calculator
- Length
- Width
- Sheet size
- Thickness
- Waste
- Price per sheet
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the area dimensions, sheet size, thickness, waste and price per sheet.
Tips for an accurate estimate
- Take measurements at floor level and at the ceiling – walls and rooms are often slightly out of square.
- Use the manufacturer’s coverage, spacing and installation data when it differs from the typical values here.
- Keep a little extra of every finish material for touch-ups and repairs later.
- Check local building codes and permits before structural, electrical, plumbing or gas work.
Common mistakes to avoid
- Sizing heating or cooling equipment by area alone when insulation, windows and climate make a big difference.
- Buying too little paint, stain or flooring and ending up with mismatched batches.
- Overlooking the extra material for steps, railings, gables and trim.
Inputs explained
| Field | What to enter |
|---|---|
| Length | Units: ft, m, in, yd, cm |
| Width | Units: ft, m, in, yd, cm |
| Sheet size | Choose one: 4 × 8 ft, 4 × 10 ft, 4 × 9 ft, 5 × 5 ft (Baltic birch) … |
| Thickness | Choose one: ¼ in (6 mm), ⅜ in (9 mm), ½ in (12 mm), ⅝ in (15 mm) … |
| Waste | In % |
| Price per sheet | Units: /piece |
What each result means
- Area = [Length]×[Width]
- Sheets = ceil([Area]×(1 + [Waste]÷100)÷[Sheet size])
- Approximate weight = [Sheets]×[Sheet size]×[Thickness]×550
- Cost = [Sheets]×[Price per sheet]
Example values
How the main result changes when Length changes and everything else stays at the example values above:
| Length (ft) | Sheets |
|---|---|
| 12 | 7 |
| 18 | 10 |
| 24 | 14 |
| 30 | 17 |
| 36 | 20 |
| 48 | 27 |
Formula
Sheets = ceil(area × (1 + waste) ÷ sheet area)Weight ≈ sheets × sheet area × thickness × 550 kg/m³Worked example
Inputs — Length: 24 ft; Width: 16 ft; Sheet size: 4 × 8 ft; Thickness: ¾ in (18 mm); Waste: 10 %; Price per sheet: $45 /piece.
Results — Area = 384 ft²; Sheets = 14; Approximate weight = 961 lb; Cost = $630.00.
Frequently asked questions
How many sheets of plywood for a 24 × 16 floor?
384 ft² ÷ 32 ft² = 12 sheets, plus waste – about 14.
How much does a sheet of ¾ in plywood weigh?
About 60–70 lb (27–32 kg) for softwood plywood; OSB is a little heavier.
Which way should subfloor sheets run?
With the long edge perpendicular to the joists and joints staggered.
What formula does the Plywood Calculator use?
Sheets = ceil(area × (1 + waste) ÷ sheet area).