Roof Snow Load Calculator — Entered Depth and Density
Estimate snow mass and vertical roof load from depth, density and area, with explicit slope geometry. Does not supply design loads or a safety judgment.
Estimate the mass of an entered snow layer and its vertical gravitational load over a roof’s horizontal footprint. The calculation uses the area, depth, slope and bulk density that you provide. It supplies neither a local building-code design load nor a judgment about whether a particular roof can carry the snow.
How to use this tool
- Enter area and identify it as horizontal footprint or actual sloping surface.
- Enter roof pitch measured above horizontal.
- Enter snow depth and state whether it was measured vertically or perpendicular to the roof.
- Supply representative bulk density, then read mass and vertical load with the stated limits.
Formula
Aₕ = Aₛ cos θ; dᵥ = dₙ ÷ cos θ; mass = ρ Aₕ dᵥ; vertical load q = ρ dᵥ g₀
Aₕ is horizontal area, Aₛ surface area, dᵥ vertical depth and dₙ normal depth. Density ρ is mass per volume; g₀ is 9.80665 m/s². Pressure is shown in kPa, equivalent to kN/m² of horizontal area.
Example
A horizontal 100 m² footprint with a uniform 0.30 m vertical snow depth and 200 kg/m³ density contains 6,000 kg. Its vertical load is 0.588399 kPa, and total gravitational force is 58.8399 kN.
Frequently asked questions
Does a smaller result mean my roof is safe?
The tool makes no capacity comparison. Drifts, unbalanced accumulation, rain, ice, previous damage and building details can matter. Local design requirements and a structure’s actual condition require a separate assessment.
Can I use ground snow depth or a standard density?
Only as a clearly understood assumption. Roof conditions can differ from nearby ground conditions, and snow density changes with age and weather. The default density is an example, not a measured local value.
Is this pressure perpendicular to the roof?
No. It is vertical gravitational force divided by horizontal projected area. Slope changes geometry here; the tool does not resolve contact forces, friction, sliding or structural load combinations.
Sources
Last updated: 2026-10-30