Ski Slope Gradient Calculator

Ski slope gradient (or grade) describes how steep a slope is, expressed as a percentage. It is calculated by dividing the vertical rise by the horizontal run and multiplying by 100. A slope with 300 m of rise over 1000 m of run has a 30% gradient. It can also be expressed as an angle in degrees or as a ratio like 1 in 3.3.

Generally, green (beginner) runs have gradients below 25%, blue (intermediate) runs range from 25–40%, red (advanced) runs range from 40–60%, black diamond (expert) runs exceed 60%, and double black diamond (extreme) runs can exceed 80–100%. These thresholds vary slightly between ski resorts and countries.

Slope as an angle is measured in degrees from the horizontal plane using the arctangent of rise over run. Slope as a percentage is simply (rise ÷ run) × 100. A 45° angle equals a 100% grade. A 30° slope equals roughly a 57.7% grade. Percentages are more commonly used in skiing and road engineering, while degrees are often used in physics and surveying.

The rise is the vertical elevation difference between the top and bottom of the slope. The run is the horizontal ground distance between those two points. You can obtain these values from topographic maps, GPS devices, ski resort trail maps, or by using a clinometer and measuring tape on the actual slope.

The steepest regularly skied runs in the world, such as Harakiri in Austria and certain extreme chutes in the Alps, can exceed 78% gradient (around 38°). Competition mogul courses typically require a minimum gradient of about 27° (roughly 51%), and extreme freeride terrain regularly exceeds 45° (100% gradient).

A 1-in-X ratio means that for every 1 unit of vertical rise, there are X units of horizontal run. For example, a 1-in-5 slope means for every metre you rise, you travel 5 metres horizontally. This format is common in civil engineering and trail design. A 1-in-5 ratio equals a 20% gradient and approximately 11.3°.

Gradient directly affects skier speed, control, and safety. Trails that are too steep for their intended difficulty classification create dangerous conditions, while under-graded slopes may be boring for advanced skiers. Gradient also affects snowmaking efficiency, drainage, and erosion risk. Proper grading ensures trails meet international ski safety standards.

The true slope length (or slope distance) is the actual distance you travel along the surface of the hill, accounting for both the rise and the run. It is calculated using the Pythagorean theorem: √(rise² + run²). It is always longer than the horizontal run and represents the actual skiing distance, which matters for trail planning and lift capacity estimates.