This plywood load capacity calculator is a vital tool for engineers, architects, and DIY enthusiasts to determine the maximum weight a plywood sheet can safely support.
When you’re building a storage loft in your garage. You need to know if a 3/4-inch plywood sheet spanning 48 inches can hold the weight of your holiday decorations. A load capacity calculator would take these parameters and output the maximum distributed load the plywood can bear, ensuring your project’s safety and longevity.
Plywood Load Capacity Calculator
| Thickness (inches) | Span (inches) | Width (inches) | Bending Stress (psi) | Max Pressure (PSF) | Load Capacity (lbs/sq ft) |
|---|---|---|---|---|---|
| 0.25 | 16 | 48 | 800 | 16 | 48 |
| 0.375 | 20 | 48 | 1000 | 22 | 66 |
| 0.5 | 16 | 48 | 1200 | 35 | 93.75 |
| 0.625 | 24 | 48 | 1350 | 45 | 105.47 |
| 0.75 | 24 | 48 | 1500 | 79 | 117.19 |
| 1 | 32 | 48 | 1800 | 160 | 131.84 |
| 1.25 | 36 | 48 | 2000 | 200 | 145.00 |
| 1.5 | 40 | 48 | 2200 | 250 | 160.00 |
| 2 | 48 | 48 | 2500 | 300 | 200.00 |
Plywood Load Capacity Chart
| Plywood Thickness (inches) | Span (inches) | Grade | Max Load (lbs/sq ft) |
|---|---|---|---|
| 1/4 | 16 | A-C | 5 |
| 1/4 | 24 | A-C | 3 |
| 1/2 | 16 | A-C | 35 |
| 1/2 | 24 | B-C | 20 |
| 3/4 | 16 | A-A | 50 |
| 3/4 | 24 | B-C | 40 |
| 3/4 | 32 | A-B | 30 |
| 1 | 24 | A-A | 164 |
| 1 | 36 | B-B | 150 |
| 1.25 | 36 | A-B | 200 |
| 1.5 | 48 | A-A | 250 |
| 2 | 48 | B-C | 300 |
Plywood Load Capacity Formula
The formula is:
Load Capacity = (F * b * d^2) / (9 * L^2)Where:
- F = Allowable bending stress (psi)
- b = Width of the plywood sheet (inches)
- d = Thickness of the plywood (inches)
- L = Span between supports (inches)
Let’s calculate the load capacity of a 4×8 foot sheet of 3/4-inch plywood spanning 24 inches:
- F = 1500 psi (typical for construction-grade plywood)
- b = 48 inches (4 feet)
- d = 0.75 inches
- L = 24 inches
Plugging these values into our formula:
Load Capacity = (1500 * 48 * 0.75^2) / (9 * 24^2) ≈ 117 lbs/sq ftHow Much Weight Will Plywood Hold?
The plywood is stronger when the load is applied perpendicular to the face grain.
Consider a scenario where you’re using 3/4-inch CDX plywood for a roof. If the rafters are spaced 24 inches apart, the plywood might safely support a uniform load of about 100 lbs per square foot. However, this capacity would decrease significantly if the span increased to 48 inches.
You should remember that point loads (concentrated weights) can dramatically reduce the overall capacity. A 200-pound person standing on a small area of the plywood might exceed its local load capacity, even if the total weight on the sheet is within limits.
What is the Load Carrying Capacity of Plywood?
A sheet of 1/2-inch plywood used as subflooring safely carry 100 lbs per square foot when joists are spaced 16 inches apart. The same plywood used vertically as wall sheathing could potentially support much higher loads due to different stress distribution.
How Much Can 3/4 Plywood Hold Per Square Foot?
3/4-inch plywood is a popular choice for many construction projects due to its strength and versatility.
Assume we’re using 3/4-inch tongue-and-groove plywood as flooring with joists spaced 24 inches on center. In this configuration, the plywood might safely support a uniform load of 150-200 lbs per square foot.
If we increase the joist spacing to 48 inches, the load capacity could drop to around 50-75 lbs per square foot. This illustrates the significant impact that span has on load-bearing capacity.
References
- APA – The Engineered Wood Association. “Plywood Design Specification.” https://www.apawood.org/plywood
- American Wood Council. “Wood Design Package.” https://awc.org/codes-standards/publications/nds-2018
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