Snow Load Weight Calculator (Roof)
Weight of the snow lying on a roof, per square metre and in total, from the depth of snow and its density.
Results
The dashed line marks the value you entered.
What this tool does
Snow is mostly air, so its weight depends far more on density than on depth: fresh powder is roughly 50–150 kg/m³, settled snow 200–400 kg/m³ and wet, soaked snow up to about 500 kg/m³. A hand's width (10 cm) of fresh snow weighs little, but 30 cm of wet snow on a roof is around 1.5 kN/m² — about the weight of two adults on every square metre. This is the weight of snow actually lying there, not a design value: building design uses regional characteristic snow loads from the standard, such as Eurocode 1 part 1-3, with shape and exposure factors.
Formula
load (kN/m²) = depth × density × g ÷ 1000 · total = load × roof area
Variables
| Symbol | Meaning | Unit |
|---|---|---|
d | Depth of snow | cm |
ro | Density of the snow | kg/m³ |
ar | Roof area, seen from above | m² |
LD | Snow load on the roof | kN/m² |
KG | Mass of snow per square metre | kg/m² |
TT | Total weight of the snow on the roof | kN |
TM | Total mass of snow | t |
Worked example
- Depth of snow30 cm
- Density of the snow200 kg/m³
- Roof area, seen from above60 m²
- Snow load on the roof0.59 kN/m²
- Mass of snow per square metre60 kg/m²
- Total weight of the snow on the roof35.3 kN
- Total mass of snow3.60 t
Limitations
- Density changes with temperature, moisture and composition. Use a value from the supplier's data sheet whenever precision matters.
- For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.