How to Use the Roof Snow Load Calculator
After a heavy snowfall, it's natural to wonder how much weight is sitting on your roof. Snow density varies enormously depending on its condition, so depth alone doesn't tell you the actual weight. Enter the snow depth, the snow's density (fresh powder, wet/settled snow, or a custom value), and your roof area, and this calculator returns both the load per square foot (psf) and the total load across the whole roof (lb).
The formula is pure physics: density × depth × area. Fresh, dry powder snow is light, at roughly 7 lb/ft³, while snow that's absorbed rain or settled and packed down can reach 20 lb/ft³ or more — nearly three times heavier for the same depth. That's why the same visible snow depth can mean very different loads depending on conditions.
Keep in mind this is a theoretical load from pure physics, not a code-compliant design value. Actual construction must follow local building code requirements — in the US, that means ASCE 7 ground and roof snow load values, which factor in site-specific conditions like exposure and roof slope. Treat this calculator as a way to estimate the weight of snow currently sitting on your roof, not as an engineering design figure.
Frequently Asked Questions
Fresh, dry powder snow is light, but rain-soaked or settled/packed snow can be three times denser and much heavier.
No — this uses pure physics (density × depth × area). Actual construction must follow local code requirements like ASCE 7 ground/roof snow load values, which include site-specific factors.
Roof structural capacity is usually rated in pounds per square foot (psf), so this lets you compare directly against your roof's rated capacity.