Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Estimated roof snow load
18.9
Ground-equivalent load
27.0
% of rated roof capacity
63%
Status
Monitor closely
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter snow depth (in).
- 2Enter snow type.
- 3Enter roof rated capacity (psf).
- 4Read your estimated roof snow load on the right — it updates as you type.
- 5Hit Share to keep the scenario or send it to someone.
About this calculator
Snow load is measured as weight per square foot, not depth, because snow density varies enormously — fresh powder runs about 7-10 lb/ft³ while wet, settled, or rain-soaked snow can exceed 20 lb/ft³. This calculator estimates load from snow depth and a density you select (or measure directly with a scale and known-volume container), then applies the standard roof exposure and thermal factors used in ASCE 7 snow load calculations to convert ground snow load to roof snow load. Most residential roofs are designed for 20-40 psf depending on region; if your estimated load approaches or exceeds your roof's rated capacity, that's a signal to shovel or call a structural engineer, not a DIY judgment call.
Worked example
Using the values the calculator loads with:
Inputs
- Snow depth: 18 in
- Snow type: Wet snow (~18 lb/ft³)
- Roof rated capacity: 30 psf
Results
- Estimated roof snow load: 18.9
- Ground-equivalent load: 27
- % of rated roof capacity: 63%
- Status: Monitor closely
What each field means
Inputs
- Snow depth (in)
- The snow depth used in the calculation, measured in in. Starts at 18 in so you have a working example on load. Accepted range: 1–120 in.
- Snow type
- Pick the option that matches your situation — the maths changes per option. Choices: Fresh powder (~8 lb/ft³), Settled/packed (~15 lb/ft³), Wet snow (~18 lb/ft³), Rain-soaked/ice-heavy (~25 lb/ft³).
- Roof rated capacity (psf)
- The roof rated capacity used in the calculation, measured in psf. Starts at 30 psf so you have a working example on load. Accepted range: 10–100 psf.
Results
- Estimated roof snow load
- Returned as a whole number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Ground-equivalent load
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- % of rated roof capacity
- Returned as a percentage. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Status
- Returned as a plain value. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
Why is roof load estimated as only 70% of ground snow load?
Wind exposure on roofs sheds and redistributes snow that would otherwise accumulate on the ground, so building codes (ASCE 7) apply an exposure factor, typically around 0.7 for a fully exposed roof, before further adjusting for thermal and building-use factors.
How do I find my roof's actual rated capacity?
Check building plans or permits for your local snow load requirement, usually stated in your jurisdiction's building code adopted from ASCE 7 tables; older homes may have been built to lower legacy standards, so when in doubt have a structural engineer verify it.
Why does wet snow matter so much more than fresh powder at the same depth?
Wet or rain-soaked snow can be 2-3 times denser than fresh powder at identical depth, meaning an 18-inch wet snowpack can weigh as much as a 45-50 inch powder snowpack — depth alone is a poor predictor of structural risk.
What are warning signs my roof is overloaded right now?
Sagging ceiling tiles, new cracks in drywall near roof lines, doors or windows that suddenly stick, popping or cracking sounds, and visible roof deflection when viewed from outside are all signs to evacuate the area below and call a professional immediately.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Snow Load on Roof Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/snow-load-roof
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/snow-load-roof" target="_blank" rel="noopener">Snow Load on Roof Calculator — RevenueLab</a> (2026).</p>
Source: [Snow Load on Roof Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/snow-load-roof) (2026).