A foot of fresh snow weighs from about 3 lb per square foot when light and dry to 21 lb per square foot when wet and heavy, and a foot of ice about 57 lb, according to FEMA’s Snow Load Safety Guide. The chart scales those figures by depth, and the calculator gives the total on a roof.
Snow and ice weight per square foot, by depth
| Depth | Light, dry snow (lb/sq ft) | Wet, heavy snow (lb/sq ft) | Ice (lb/sq ft) |
|---|---|---|---|
| 1 in | 0.3 | 1.8 | 5 |
| 2 in | 0.5 | 3.5 | 10 |
| 3 in | 0.8 | 5.3 | 14 |
| 4 in | 1.0 | 7.0 | 19 |
| 6 in | 1.5 | 10.5 | 29 |
| 8 in | 2.0 | 14.0 | 38 |
| 10 in | 2.5 | 17.5 | 48 |
| 12 in | 3.0 | 21.0 | 57 |
| 18 in | 4.5 | 31.5 | 86 |
| 24 in | 6.0 | 42.0 | 114 |
| 30 in | 7.5 | 52.5 | 143 |
| 36 in | 9.0 | 63.0 | 171 |
| 48 in | 12.0 | 84.0 | 228 |
Snow load calculator
Ground snow, roof snow and design load
- Roof load is not ground load. FEMA notes that roof snow loads differ from ground snow and depend on wind exposure, roof slope and shape, obstructions, the building’s heat and its use. Drifts and snow sliding from a higher roof can load one area far more than the average.
- Know the design snow load. FEMA says it can be found on the construction drawings; if there are none, have a licensed design professional determine the roof’s capacity before the season.
- Ice and refrozen melt are heavy. One inch of ice weighs about as much as a foot and a half of light snow, and melt water that pools and freezes concentrates the load.
- Sagging ceiling boards or tiles, or sagging sprinkler lines and heads
- Popping, cracking and creaking noises
- Sagging roof members or sheathing, bowing truss chords or webs, cracked or split wood members
- Doors or windows that no longer open or close, cracks in walls or masonry, severe roof leaks
- If you see these, FEMA says to evacuate the building promptly and have a qualified design professional, such as a Professional Engineer, inspect it.
Related: construction calculators and the wind chill chart for working outside in winter.
Frequently asked questions
How much does a foot of snow weigh per square foot?
From about 3 lb/sq ft for light, dry snow to 21 lb/sq ft for wet, heavy snow (FEMA).
How much does snow weigh per cubic foot?
The same numbers: about 3 lb for light, dry snow up to 21 lb for wet, heavy snow, and about 57 lb for ice.
How much snow can my roof hold?
It depends on the design snow load the roof was built for, which is on the construction drawings or can be determined by a licensed engineer. Compare it with the load from this chart, allowing for drifts.
Sources
- Federal Emergency Management Agency. FEMA P-957, Snow Load Safety Guide (January 2013), sections 2.1, 2.2, 2.3, 4.2, 4.3 and 5.1-5.3, published by the US Government Publishing Office at govinfo.gov. A US Government work.
Last reviewed: 12 November 2026. Numbers in the tables are our arithmetic from the sources listed. How we check our work: methodology and corrections. Spotted an error? Please let us know.