Snow Load Calculator
Calculate the total weight of snow on your roof in pounds and pounds per square foot (psf). Get a safety rating based on typical residential roof capacity.
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Total Weight
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Weight per Sq Ft (psf) —
Risk Level —
Extended More scenarios, charts & detailed breakdown ▾
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psf
Total Weight
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Snow Load (psf) —
Max Safe Snow Depth —
Status —
Professional Full parameters & maximum detail ▾
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psf
ASCE 7 Loads
Flat Roof Snow Load Pf (psf) —
Slope Factor Cs —
Balanced Load Ps (psf) —
Unbalanced Load (psf) —
Structural
Total Balanced Load (lbs) —
Capacity Margin —
How to Use This Calculator
- Enter the roof dimensions in feet.
- Enter snow depth in inches.
- Select the snow type to use the correct density.
- Results show total weight, pounds per square foot, and a risk level.
Formula
Weight (lbs) = Area (sq ft) × Depth (ft) × Snow Density (pcf)
Densities: Fresh snow = 5 pcf | Packed = 20 pcf | Wet = 15 pcf | Ice = 57 pcf
PSF = Weight ÷ Area | Risk: <20 psf = Safe, 20-40 psf = Caution, >40 psf = Danger
Example
Example: 30 ft × 40 ft roof, 18 inches packed snow → 1,200 sq ft × 1.5 ft × 20 pcf = 36,000 lbs (30 psf) → Caution.
Frequently Asked Questions
- Fresh snow weighs about 3 psf per foot of depth, packed snow about 20 psf per foot, and ice about 57 psf per foot. Wet snow falls between 12-20 psf per foot.
- Most residential roofs are designed for 20–40 psf live load. If you exceed 20 psf, consider removing snow. Consult a structural engineer for your specific building.
- Remove snow when the load exceeds 20 psf, especially on flat or low-pitch roofs, older structures, or buildings showing signs of stress (cracking, creaking, doors sticking).
- Yes — steeper roofs shed snow naturally. Slopes over 70° are assumed to carry zero snow. The slope reduction factor (Cs) reduces the balanced load on pitched roofs.
- Ground snow load (pg) is the weight of snow on the ground, measured in psf. Roof loads are typically 70-100% of ground loads depending on slope, exposure, and thermal factors.