Excavation slope calculator
Work out the top width, horizontal run and angle of a symmetrical excavation from an assessed slope ratio.
Enter your values
Check this tool fits your task
Straight, equal slopes on both sides with a flat bottom. The slope is an input from a competent design or assessment; this tool does not choose a protective system or declare ground safe.
Your result
Enter your values, or try the example to see how it works.
Calculation breakdown
What to do next
Method and sources
Run per side = depth × H:V ratio. Top width = bottom width + 2 × run. Angle above horizontal = arctan(1 ÷ ratio).
OSHA excavation Appendix B: H:V convention and design limitations ↗
How to use this tool
- Check the scope and collect measured or verified input values.
- Enter values using the displayed units, then calculate.
- Read the result, calculation breakdown and next steps together.
Worked example
Fictional geometry: 2 m depth, 1 m bottom, 1.5H:1V on each side → 3 m run per side and 7 m top width. This is not a recommended slope for your excavation.
The example button fills illustrative values. Where a scope confirmation is shown, check it yourself before calculating.
Method and references
Run per side = depth × H:V ratio. Top width = bottom width + 2 × run. Angle above horizontal = arctan(1 ÷ ratio).
Straight, equal slopes on both sides with a flat bottom. The slope is an input from a competent design or assessment; this tool does not choose a protective system or declare ground safe.
Common questions
Does choosing 1.5H:1V make the trench safe?
No. Geometry alone cannot assess soil, water, loading, nearby structures or protective-system adequacy.
Can I use this for benches or unequal sides?
No. It models one straight symmetrical cross-section only.
Does the tool classify soil?
No. Soil classification and system design require competent assessment under the applicable rules.
Public beta · Check the method and inputs with a competent reviewer before operational use.
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