Roof Snow Weight Calculator
Last reviewed How we calculate
Snow is heavier than it looks, and wet snow can weigh several times as much as fresh powder. This works out what the snow on a roof weighs, per square foot and in total, from its depth and type.
Weight of the snow on your roof
How much the snow on your roof weighs, per square foot and in total.
This calculator needs JavaScript to work. The measurements below are the ones you would need to do the sum by hand.
Load on the roof
- Load per square meter
- Total weight on the roof
This is the weight of the snow on the roof now, not the load the roof was designed for. Design snow loads come from local code and depend on your area, the roof shape and drifting. If you see sagging, new ceiling cracks or doors that start to stick, get everyone out and call a professional. Never climb onto a snow-covered roof: clear it from the ground with a roof rake, or have a professional do it.
How the calculation works
Multiply the depth of the snow in feet by its density in pounds per cubic foot to get the load in pounds per square foot. Multiply by the plan area of the roof for the total weight. The densities offered are typical figures, and real snow varies a great deal with temperature, wind and how long it has been lying.
A worked example
A foot of settled snow at about 19 lb per cubic foot puts about 19 lb on every square foot of roof, or about 93 kg per square meter. On a roof covering 1,500 sq ft, that is about 28,500 lb of snow.
This is not a design load
A roof’s capacity is set by the design snow load in your local building code, which depends on where you live, the roof shape, and how snow drifts and slides on it. This calculator cannot tell you whether a roof is safe. Drifts against walls and higher roofs, and snow that slides onto a lower roof, can load one area far more than the average.
Safety
Warning signs of an overloaded roof include sagging, new cracks in ceilings or walls, creaking, and doors or windows that suddenly stick. If you see them, get everyone out of the building and call a professional. Do not climb onto a snow-covered roof to clear it. Use a roof rake from the ground, or have a professional do it.
Frequently asked questions
How heavy is a foot of snow on a roof?
It varies a lot with the type of snow. Typical figures are around 6 pounds per square foot for a foot of fresh snow, about 19 for settled snow, and about 25 for wet, heavy snow.
How do I know how much snow my roof can hold?
Roofs are designed for a snow load set by the local building code for your area and roof shape. Your building department, the house plans or a structural engineer can tell you the design load.
Should I clear snow off my roof myself?
Not by climbing onto it. Use a roof rake from the ground, or have a professional clear it. If you see sagging, new ceiling cracks or doors that suddenly stick, get everyone out and call for help.