Quick answer
According to FEMA, a foot of fresh snow weighs 3 lb per square foot when light and dry and 21 lb per square foot when wet and heavy. An inch of ice adds a little under 5 lb per square foot. A foot of wet snow on a roof with a 1,500 sq ft footprint weighs about 31,500 lb.
Snow weight by depth
FEMA's Snow Load Safety Guide (P-957) puts fresh snow at 3 lb per square foot per foot of depth when light and dry and 21 lb when wet and heavy. Scaled to common depths:
| Snow depth on the roof | Light, dry | Wet, heavy | Wet snow on a 1,500 sq ft footprint |
|---|---|---|---|
| 6" | 1.5 lb/sq ft | 10.5 lb/sq ft | 15,750 lb |
| 12" | 3 lb/sq ft | 21 lb/sq ft | 31,500 lb |
| 18" | 4.5 lb/sq ft | 31.5 lb/sq ft | 47,250 lb |
| 24" | 6 lb/sq ft | 42 lb/sq ft | 63,000 lb |
| 36" | 9 lb/sq ft | 63 lb/sq ft | 94,500 lb |
Use the house footprint, overhangs included, not the sloped roof area: snow falls straight down. Both figures are for fresh snow. Roof snow in the sun can soften, become denser and then harden when it freezes, and meltwater can pool and refreeze into ice, so for snow that has sat on the roof, use the wet column at least.
Ice is the heavy part
FEMA puts an inch of ice at a little under 5 lb per square foot and a foot of ice at about 57. Inch for inch, that is far heavier than wet snow, which is part of why FEMA stresses preventing ice buildup on a roof. The roof snow load calculator adds an ice layer to the snow for you.
Why the snow in your yard is a poor guide
FEMA warns that measuring the snow on the ground and assuming the roof carries the same is incorrect. The load on a roof depends on wind exposure, the roof's slope and shape, anything sticking up through it, and how warm the building is. Wind also drifts snow into valleys and against walls, and FEMA notes that an uneven load like that is a greater risk to the roof structure than a uniform one.
Your roof's design snow load
That is its design snow load, set when it was built. FEMA's guide says to find it on the construction drawings, or to have a licensed design professional work it out if there are none. Older roofs may have been designed for less: drifting snow loads only entered the building codes in 1975 in the East and Midwest, and 1988 in the West.
Signs a roof is overloaded
- Sagging ceilings or a sagging roof line
- Popping, cracking or creaking sounds
- Doors or windows that suddenly won't open or close
- New cracks in walls, or split framing
- Severe roof leaks
FEMA's advice if you see any of these: get everyone out of the building and have a structural engineer inspect it.
Clearing snow off the roof
FEMA notes that most buildings are not at risk from snow, and that climbing up to remove it is often more dangerous than leaving it. If it does need to come off, FEMA recommends a licensed, insured roofing contractor who has removed roof snow before. If you rake it yourself, stay on the ground with a non-metal roof rake and keep well back from the eave, because roof snow can slide at any moment. Leave at least 2 inches on the roof so the roofing isn't damaged, and if there is any sign the roof could collapse, stop and get everyone out.
Frequently asked questions
How much does a foot of snow weigh?
About 3 lb per square foot for light, dry fresh snow and 21 lb per square foot for wet, heavy snow, according to FEMA.
How much does a foot of wet snow weigh on a whole roof?
On a roof with a 1,500 sq ft footprint, about 31,500 lb, or 15.8 tons, at FEMA's 21 lb per square foot per foot.
How much does ice weigh on a roof?
A little under 5 lb per square foot for each inch, and about 57 lb per square foot for a foot of ice, according to FEMA.
When should snow be removed from a roof?
FEMA says removal is prudent when the load is close to the roof's design capacity, or somewhat close with more snow forecast. Most buildings never get there. If yours might, FEMA recommends a licensed, insured roofing contractor rather than climbing up yourself.
Calculators for this
Roof Snow Load
How much does the snow on your roof weigh?
Roofing Shingle
Estimate roof area from your house footprint and pitch, then get squares, shingle bundles, nails, underlayment, drip edge and cost.
Rafter Length & Roof Pitch
Get common rafter length from building width and roof pitch, with overhang, roof angle, plumb and seat cuts and a to-scale drawing.
Published 2026-10-30. Sources: FEMA P-957, Snow Load Safety Guide (January 2013). See how we calculate.