Snow Roof Load
Calculator
Results
- Snow load (kg/m²)
- 100
- Snow load (kPa)
- 0.980665
- Total snow mass on the roof (kg)
- 10,000
Weather results
| Snow load (kg/m²) | 100 |
| Snow load (kPa) | 0.980665 |
| Total snow mass on the roof (kg) | 10,000 |
formula-map diagram
- Snow load (kg/m²)
- 100
- Snow load (kPa)
- 0.980665
- Total snow mass on the roof (kg)
- 10,000
Weather relationship
Formula
load (kg/m²) = depth (m) × ρ_snow; pressure (kPa) = load × g ÷ 1000, g = 9.80665 m/s²= 100
Note
This is a simplified model: it applies the published standard formula to the numbers you entered and ignores local terrain, radiation, precipitation type and instrument error. Wind chill is the 2001 NWS/Environment Canada regression, valid at or below 10 °C with wind at or above 4.8 km/h; the heat index is the Rothfusz regression, reliable above about 27 °C; dew point uses the Magnus approximation (a = 17.27, b = 237.7 °C) over liquid water; wet bulb uses Stull's approximation at standard sea-level pressure; pressure and density altitude assume the International Standard Atmosphere and dry air. Do not use these results for aviation, structural or safety decisions without an official forecast or a qualified professional.
More in Weather and climate
See all →Frequently asked questions
How is the structural load from snow on a roof calculated?+
It's the snow water equivalent (the depth of water the snow would produce if melted) multiplied by the density of water, giving a load per unit area, since water weighs a known, fixed amount (about 1 kg per litre, or roughly 5.2 pounds per square foot per inch of water depth).
Why can't roof snow load be estimated from snow depth alone?+
The same depth of snow can weigh dramatically different amounts depending on whether it's light, fresh powder or dense, wet, or partially melted and refrozen snow, so depth alone, without a density or water-equivalent figure, gives an unreliable load estimate.
Why is wet, settled snow more dangerous for roofs than fresh powder of the same depth?+
Wet or settled snow has absorbed additional water or compacted under its own weight, raising its density and therefore its load per unit depth substantially above fresh powder, so a roof that safely held a fresh snowfall can become overloaded as that same snow settles, gets rained on, or partially melts and refreezes.
How does roof pitch affect actual snow load compared to the calculated ground or flat-roof value?+
Steeper roofs tend to shed snow more readily by sliding, reducing the accumulated load relative to a flat roof exposed to the same snowfall, which is why building codes typically apply a roof slope reduction factor to the base ground or flat-roof snow load figure.
Why do engineers care about this calculation for structural safety?+
Roofs are designed to a maximum specified snow load; if actual accumulated snow (accounting for density, drifting, and any rain-on-snow events) exceeds that design value, structural failure becomes a real risk, which is why monitoring snow load, not just snow depth, matters for older or heavily-loaded roofs during major snow events.