Free Snow Load Tool

Roof Pitch Calculator Snow Load

This roof pitch calculator for snow load determines the actual snow weight on a sloped roof using ASCE 7 (Minimum Design Loads for Buildings) methodology. Ground snow load is reduced by the roof slope factor (Cs): a 6:12 pitch reduces balanced snow load by approximately 15%, while a 12:12 pitch reduces it by up to 60%. Fresh snow weighs 5–20 lbs/sq ft per foot of depth; packed snow weighs 20–40 lbs/sq ft. The calculator computes balanced and unbalanced snow loads per ASCE 7-22 Section 7.

ac_unit Snow Load by Roof Slope

❄ ❄ ❄ ❄ 23.8 psf
Slope Factor (Cs)0.85
Load Reduction15%
SheddingModerate
ac_unit Snow Load Inputs
psf
: 12
sq ft
monitor_weight Snow Load Results
Flat Roof Load (Pf)—
Slope Factor (Cs)—
Sloped Roof Load (Ps)—
Load Reduction—
Total Snow Weight—
Slope Angle—

How to Calculate Snow Load by Roof Pitch

Snow load calculation starts with the ground snow load (Pg) for your location, then applies exposure, thermal, and slope factors. Steeper pitches shed snow faster, reducing the roof snow load.

tune Drag the Slider to Change Pitch
Run Rise Slope 26.57°
0.5:12 24:12
Angle 26.57°
Grade 50.0%
Multiplier 1.118
Type Conventional
1
ac_unit

Find Ground Snow Load

2
thermostat

Determine Thermal & Exposure Factors

3
calculate

Apply Slope Factor

Snow Load Formulas

ASCE 7 snow load calculation formulas for sloped roofs:

straighten Flat Roof Snow Load
Pf = 0.7 × Ce × Ct × Is × Pg
0.7 × 1.0 × 1.0 × 1.0 × 40 psf = 28 psf
rotate_right Sloped Roof Snow Load
Ps = Cs × Pf
0.85 × 28 psf = 23.8 psf (at 6:12 pitch)
percent Snow Weight
Weight = Ps × Roof Area
23.8 psf × 2,000 sq ft = 47,600 lbs total
science Live Formula Calculator
ft
ft
Pitch 6 : 12
Angle 26.57°
Grade 50.0%
Rafter 13.42 ft
Multiplier 1.118

Snow Load Reduction by Pitch Chart

Click any row to see the pitch angle visualized. The chart covers all standard pitches from flat (1:12) to steep (12:12) with walkability ratings, material compatibility, and snow shedding performance.

Pitch Angle Grade Multiplier Type Walkability Snow Shedding
1:12 4.76° 8.3% 1.003 Flat/Low Easy Poor
2:12 9.46° 16.7% 1.014 Low Slope Easy Poor
3:12 14.04° 25.0% 1.031 Low Slope Easy Fair
4:12 18.43° 33.3% 1.054 Conventional Easy Fair
5:12 22.62° 41.7% 1.083 Conventional Easy Good
6:12 26.57° 50.0% 1.118 Conventional Moderate Good
7:12 30.26° 58.3% 1.158 Conventional Caution Very Good
8:12 33.69° 66.7% 1.202 Conventional Caution Very Good
9:12 36.87° 75.0% 1.250 Steep Unsafe Excellent
10:12 39.81° 83.3% 1.302 Steep Unsafe Excellent
11:12 42.51° 91.7% 1.357 Steep Unsafe Excellent
12:12 45.00° 100.0% 1.414 Steep Unsafe Excellent
6:12 — 26.57°
Compatible: All Types

FAQs

Answers to the 14 most common questions about roof pitch, slope angle, walkability, snow load, and roofing materials.

What roof pitch sheds snow best?

Roof pitches of 6:12 (26.6°) and steeper effectively shed snow. A 6:12 pitch reduces snow load by approximately 15%. A 12:12 pitch (45°) reduces snow load by up to 60%. Metal roofs shed snow at lower pitches than asphalt due to the slippery surface.

How much does snow weigh on a roof?

Fresh snow weighs 5–20 lbs per cubic foot; packed snow weighs 20–40 lbs per cubic foot; ice weighs 57 lbs per cubic foot. One foot of fresh snow on a 2,000 sq ft roof can weigh 10,000–40,000 lbs (4,536–18,144 kg).

What is the minimum roof pitch for snow?

A minimum pitch of 3:12 (14°) is recommended in snow-prone regions for asphalt shingles. Metal roofs perform well at 2:12 (9.5°) or steeper. Pitches below 3:12 in heavy snow zones require engineered structural capacity for full ground snow load.

How do I find my ground snow load?

Ground snow load (Pg) is found in ASCE 7 Figure 7.2-1 or your local building code. Values range from 0 psf in southern states to 300+ psf in mountainous regions. Your local building department provides the site-specific value.

Does roof material affect snow shedding?

Yes, smooth materials shed snow at lower pitches. Metal roofs shed snow at 3:12 (14°), asphalt shingles require 6:12 (26.6°), and textured surfaces like wood shake need 8:12+ (33.7°+) for reliable shedding.

What is an unbalanced snow load?

Unbalanced snow load occurs when wind redistributes snow to one side of a ridge or against obstructions. The leeward side can accumulate 1.5–3× the balanced load. ASCE 7 requires checking both balanced and unbalanced conditions.