Snow Load Calculator
Weight of snow on a roof from depth and snow type, in kPa and psf.
About this tool
Enter the snow depth and pick a snow type (or a measured density), then the roof area. The tool shows the load per square metre and square foot and the total weight of snow on the roof.
How heavy is snow?
Snow's weight depends on its density: fresh powder is roughly 100 kg/m³, settled snow about 300, wet snow 400–500 and ice 917. The load is depth × density × gravity, so 30 cm of settled snow is 90 kg/m², about 0.88 kPa or 18.4 lb/ft², and over a 100 m² roof that's 9 tonnes. For a better estimate, cut a known volume of snow from the roof, weigh it and enter the measured density. Drifts against walls, behind parapets and in valleys can be several times the average depth, and rain falling on snow soaks in and adds weight quickly. Honest limits: this estimates the snow actually present; design snow loads come from local building codes such as ASCE 7 or Eurocode 1, which add exposure, thermal and slope factors, and only a structural engineer can say what a particular roof can carry. Not safety or engineering advice: if a roof sags or creaks, leave and call a professional. The roofing calculator and the density calculator are related.
Frequently asked questions
How much does a foot of snow weigh on a roof?
Light fresh snow is about 6 lb/ft² per foot of depth; settled snow about 18 to 19 lb/ft²; wet snow 28 lb/ft² or more.
How do I calculate snow load?
Multiply depth in metres by snow density in kg/m³ to get kg/m², then by 9.81 and divide by 1,000 for kPa.
What is the density of snow?
From about 50 to 100 kg/m³ for fresh powder to 400 to 500 kg/m³ for wet or packed snow.
Can this tell me if my roof is safe?
No. A roof's capacity depends on its design and condition; only a structural engineer can assess it.
Is my data sent anywhere?
No. Everything is calculated in your browser, and nothing is stored or sent.