Roof Snow Load Calculator
Enter the roof footprint, the snow depth and the snow type. The calculator gives total weight, pounds per square foot against the 20 psf residential design line, and a plain verdict.
The question after every monster storm: how much is too much on the roof? Most houses are engineered for about 20 pounds per square foot, wet snow runs 20 pounds per cubic foot, and the arithmetic is simple - which is exactly why doing it beats guessing while the trusses creak.
How to use
- Roof footprint - the house footprint is close enough for the verdict.
- Snow depth from a ruler, averaged over the flat sections.
- Snow type: powder, wet, or the packed icy shell that arrives in March. The verdict updates live.
Frequently asked questions
How much snow can a residential roof hold?
Most are engineered for roughly 20 pounds per square foot - about 4 feet of fresh powder, 1 foot of wet snow, or 8 inches of the packed icy stuff. The calculator converts your actual depth and snow type into psf so the verdict means something.
How do I calculate snow load on a roof?
Depth in feet times snow density in pounds per cubic foot gives psf; multiply by the footprint for total weight. A 1,500 square foot roof under a foot of wet snow carries about 30,000 pounds - seven parked SUVs of load. The page does this arithmetic live.
When should I rake snow off the roof?
When psf approaches the 20 design line, when you hear popping or creaking, or when doors start sticking - and always from the ground with a roof rake, focused on the bottom four feet near the eaves. Nobody should climb an icy roof to save shingles.
What is an ice dam and why does it matter?
Meltwater from the warm ridge refreezes at the cold eave and builds a ridge that ponds water under the shingles - the damage is water inside, not weight. Clean gutters in fall, rake the eave line after storms, and check the pipe freeze math for what the same freeze-thaw does to plumbing.