Slope Angle and Avalanche Risk Window

Slope angle, slope %, and 30-45 deg avalanche start-zone flag.

Run the calculator

Example

You enter

Measured angle (deg) 32

You get

Slope angle 32.0 deg
Slope % 62.5 %
30-45 deg avalanche window INSIDE

Checked against published worked examples from: American Avalanche Association / NWS avalanche-window guidance.

Details, formula, and sources

Formula or tableSlope angle (degrees) = atan(rise / run). Slope % = (rise / run) × 100. 30-45° avalanche start-zone window flagged per AIARE / USGS / Avalanche Center guidance.

Source and editionAIARE (American Institute for Avalanche Research and Education) Level 1 / 2 curriculum by name; USFS National Avalanche Center materials by name.

Free accessFree at avalanche.org and fsavalanche.org.

What governsGeometry is not forecasting. Avalanche advisory and incident commander govern.

API field namesmeasured_angle_deg, angle_deg, slope_percent, in_avalanche_window

Avalanche start-zone window 30°-45° (true slope angle)AIARE Level 1 curriculum