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ClearQuip · Outdoors & weather

Roof snow load calculator

By ZIP · ASCE 7-style simplified estimate · psf

Estimate the design snow load on a roof, in pounds per square foot (psf), from a US ZIP code, the roof pitch and how exposed the building is to wind. It's useful for planning and for understanding how the factors interact. It isn't a substitute for your local building department's figures.

Inputs

Leave blank for flat / Cs = 1.0

Result

Enter a ZIP and calculate for an estimated roof snow load.

Disclaimer: Results are estimates using a simplified ASCE 7–style method and state-level ground snow approximations. They are not sealed engineering, code compliance, or insurance advice. Local maps and a licensed design professional govern real projects.

Planning time outdoors this season? Check open-burning rules by ZIP at HikeSpan.

How to use the roof snow load calculator

  1. Enter a 5-digit US ZIP code. The tool maps it to a state and uses a typical state-level ground snow load.
  2. Optionally enter the roof pitch as rise over 12 (for example 6 for a 6:12 roof). Leave it blank for a flat or low-slope roof.
  3. Choose the exposure: sheltered by trees or taller buildings, partially exposed (typical suburban), or fully exposed on open terrain.
  4. Press Calculate to see the estimated roof load along with every factor used.

How it's calculated

Flat-roof load pf = 0.7 × Ce × Ct × I × pg
Sloped-roof load ps ≈ Cs × pf

pg is the ground snow load, Ce the exposure factor (1.2 sheltered, 1.0 partial, 0.9 exposed), Ct the thermal factor (1.0 for a heated building), I the importance factor (1.0 for ordinary buildings), and Cs the slope factor, which falls from 1.0 on low slopes to 0.6 on very steep roofs as snow slides off. Real ground snow loads vary a lot within a state, especially in mountains and lake-effect belts, so always confirm against your jurisdiction's map.

Worked example

ZIP 55401 (Minneapolis, Minnesota) uses a ground snow load of 50 psf in this tool. With partial exposure and a 6:12 roof:

FAQ

What is a typical roof snow load?

It varies enormously, from 0 psf in much of the South to well over 50 psf in northern and mountain regions. Your local building department publishes the design value for your address.

Does a steeper roof carry less snow?

Generally yes. Snow slides off steeper roofs, so design codes reduce the load with a slope factor. Obstructions, valleys and drifts can still concentrate snow.

Is this snow load calculator suitable for permits?

No. It is a simplified educational estimate. Permits and structural decisions need your jurisdiction's official values and a licensed design professional.

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