Snow Load Calculator
A metre of powder can weigh less than 20 cm of slush.
A metre of powder can weigh less than 20 cm of slush.
Total load on the roof
8,000 kg
100 kg/m² (0.98 kPa) of settled snow
Depth alone tells you almost nothing. Fresh powder runs about 70 kg/m³ and wet snow about 500 (over seven to one) so a metre of dry snow can weigh less than 20 cm of the wet snow that follows a thaw and refreeze. The load acts on the plan area, not the roof surface. Snow lies horizontally, so a pitched roof carries the weight of the footprint it covers, and only sheds it once the pitch is steep enough for the snow to slide. Snow does not lie evenly, which is where roofs actually fail. Drifts against walls, in valleys and behind parapets routinely reach two to three times the flat depth, and that is exactly the part a single depth measurement misses.
How the Snow Load Calculator works
Weight of snow on a roof from depth and density, in kilograms and kilopascals, with the pitch shedding factor and the water equivalent. It counts weight and does not design a roof.
Also known as: how much does snow on my roof weigh · snow weight per square metre · should i clear snow off my roof · snow density by type
Where to go next
The Snow Load question rarely arrives on its own. These are the ones that usually come with it:
- Shelf Sag Calculator — A front lip beats a thicker board. Depth is cubed.
- Cloud Base Calculator — The 400 ft rule, derived rather than memorised.
- Lightning Distance Calculator — Tells you where the last strike was. Not the next one.
- Speed Distance Time Calculator — Any one of the three from the other two, in four units.
Frequently asked questions
How much does snow weigh?
It depends entirely on density. Fresh powder is about 70 kg/m³ and wet snow about 500 — over seven to one — so 50 cm weighs anywhere from 35 to 250 kg per square metre.
Does depth tell me the load?
Almost nothing on its own. A metre of dry powder can weigh less than 20 cm of the wet snow that follows a thaw and refreeze, which is when roofs fail.
Does a pitched roof carry less snow?
Yes, above about 30°, because snow starts sliding. Below that the load acts on the full plan area — snow lies horizontally regardless of what the roof does.
Will my roof hold this?
This page cannot tell you. That needs the structure, the span, the local code snow map and a drift analysis, and it is a question for an engineer.
Why do drifts matter so much?
Because snow does not lie evenly. Drifts against walls, in valleys and behind parapets reach two to three times the flat depth, and that is where roofs actually fail.
Put this calculator on your own site
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Related calculators
Shelf Sag Calculator
A front lip beats a thicker board. Depth is cubed.
OpenCloud Base Calculator
The 400 ft rule, derived rather than memorised.
OpenLightning Distance Calculator
Tells you where the last strike was. Not the next one.
OpenSpeed Distance Time Calculator
Any one of the three from the other two, in four units.
Open