Snow Load Calculator
Estimate the snow load on a roof.
Fresh ~7, packed ~15, wet ~20+
Results update as you type.
How it works
Heavy snow can put dangerous weight on a roof, and this calculator estimates that load so you can gauge the risk. You enter the roof area, the depth of snow, and the snow's density, and it returns the total snow load in pounds and the load per square foot. The calculation converts the snow depth to feet, multiplies by density to get the weight per square foot, and multiplies by the roof area for the total. The critical variable is density, because not all snow weighs the same: light, fresh powder might be around 7 pounds per cubic foot, settled or packed snow around 15, and wet, heavy snow or old compacted snow 20 or more, with ice far heavier. This is why a foot of dense wet snow can weigh several times more than a foot of fluffy powder. Roofs are engineered to carry a certain snow load rated for the local climate, and exceeding it risks structural damage or collapse, so knowing the estimated load helps you decide whether to clear the roof. Standing water from melting snow and ice dams add further weight. This is an educational estimate; local building codes specify design snow loads, and a structural engineer should assess any real concern. Enter your roof area, snow depth, and density to estimate the snow load.
Load = area × (depth / 12) × snow density
The load per square foot is the snow depth in feet, found by dividing inches by twelve, times the snow's density in pounds per cubic foot. Multiplying that by the roof area gives the total weight of snow on the roof. Denser, wetter, or deeper snow dramatically increases the load, which is why heavy snowfalls threaten roofs.
Source:Structural estimation
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter roof area and snow depth.
- 2
Adjust the options
Adjust snow density if they apply — sensible defaults are already set.
- 3
Read your result
Total snow load updates instantly as you type — no button to press.
Frequently asked questions
How do I calculate snow load on a roof?
Convert the snow depth to feet, multiply by the snow's density in pounds per cubic foot to get the load per square foot, then multiply by the roof area for the total weight. The calculator does this from your inputs, giving both the per-square-foot load and the total snow weight on the roof.
What density should I use for snow?
Density varies widely with snow type. Fresh, light powder is roughly 5 to 10 pounds per cubic foot, settled or packed snow around 12 to 18, and wet, heavy snow or old compacted snow 20 or more. Ice is far denser. Use a value matching your snow's condition, since density strongly affects the load.
Why does wet snow weigh so much more?
Wet snow contains far more water per volume than dry powder, and water is heavy. A foot of soggy, dense snow can weigh three or more times as much as a foot of fluffy fresh snow. This is why roofs are most at risk during heavy wet snowfalls, rain on snow, and repeated freeze-thaw cycles.
When is snow load dangerous for a roof?
Roofs are designed for a maximum snow load set by local building codes for the region's climate. When accumulated snow, especially dense or wet snow, approaches or exceeds that rating, there is a risk of structural damage or collapse. Warning signs include creaking, sagging, or sticking doors. If in doubt, safely clear the roof or consult a professional.
Should I clear snow from my roof?
If the estimated load is high, especially with wet snow or ice dams, clearing snow can protect the roof, but do it safely, ideally with a roof rake from the ground, since climbing an icy roof is dangerous. For serious concerns or significant snow, hire professionals. This calculator estimates load but does not replace an engineer's assessment.