Formula and input notes
Estimated snow weight = roof area × (average snow depth ÷ 12) × entered snow density
| Input | Practical note |
|---|---|
| Roof area | Enter the roof area associated with the measured snow layer, not automatically the building floor area or horizontal footprint. |
| Snow density | Enter an average density for the snow layer being estimated. Wet, settled, drifted, or ice-laden snow can differ sharply from fresh snow. |
Worked snow load example
Snow Load Calculator example: 177 ft² × (12 in ÷ 12) = 177 ft³ of snow. At the entered 20 lb/ft³, the estimated total weight is 3,540 lb (1.77 short tons).
Read total snow-layer weight carefully
Use the total as a rough physical-weight illustration and compare field concerns with qualified local guidance rather than converting it directly into allowable capacity.
Why code roof snow load needs more data
Snow density varies greatly with moisture, age, drifting, rain-on-snow, ice layers, roof heat loss, and sampling location; depth alone is not a code roof load.
Questions specific to this calculation
Is snow depth times density the same as code roof snow load?
No. This tool estimates the total weight of the entered snow layer. Structural design can require ground snow data, exposure, thermal and importance factors, roof slope, drifting, sliding, unbalanced loading, rain-on-snow, and load combinations.
Which snow density should I enter?
Use a measured or otherwise defensible average for the actual layer being estimated. Fresh, settled, wind-packed, wet, and ice-laden snow can have very different densities, so a generic value can materially change the result.
For U.S. structural design parameters, use the governing code edition and site-specific data such as the ASCE Hazard Tool; the snow-layer weight here is not a design roof snow load.