Slope Width Calculator

How Slope Ratios Work

H:V notation: A slope ratio of 2:1 means 2 feet of horizontal run for every 1 foot of vertical rise (or depth). The formula is simple: Slope Width = Depth × Ratio. A 10-foot deep cut at 2:1 requires 20 feet of slope on each side.

When to use which ratio:

• 1:1 — Hard rock, very stable material. Steep, minimal right-of-way needed.
• 1.5:1 — Firm soils, compacted material, short-term cuts.
• 2:1 — Most common cut slope in average soil. Used on highway projects.
• 3:1 — Standard fill slope. Good for revegetation and erosion resistance.
• 4:1 — Gentle slope for drainage swales, mowing, or sensitive areas.

⚠️ Safety warning: Soil type has a major effect on safe slope angles. Saturated soils, loose fills, and sandy materials can fail at angles that appear stable. Always follow geotechnical recommendations and local code. Trenches over 1.5m (5 ft) require shoring or benching in most jurisdictions.

Total top width: If you enter a bottom width (e.g., the road or trench width at the base), the calculator adds two slope widths to get the total surface width at the top. This is useful for right-of-way calculations.