Input parameters
Fill inputs below and press Calculate.
Formula used
This calculator estimates a practical exclusion width for planning and daily controls.
- R = Hazard reach radius (fall, swing, debris reach).
- Cbase = Base clearance from the chosen activity preset.
- Cextra = Additional clearance you add for site constraints.
- W = Wind allowance = Wind speed × Wind allowance factor.
- S = Slope factor = 1 + (Slope % × Slope sensitivity).
- RF = Risk multiplier selected from the risk level list.
Use this estimate alongside your method statement, local rules, and competent-person review.
How to use this calculator
- Pick units and select the closest activity type.
- Enter hazard reach radius based on the main hazard.
- Add extra clearance for people, tools, barriers, or access.
- Enter wind and slope if they can influence the hazard.
- Select risk level to reflect site complexity and exposure.
- Press Calculate and apply the width to your cordon layout.
- Download CSV or PDF for briefings and documentation.
Example data table
A sample scenario with lifting operations and a higher risk setting.
| Input | Value | Unit |
|---|---|---|
| Units | Metric | m |
| Activity type | Lifting & Rigging | - |
| Risk level | High | - |
| Hazard reach radius | 6.00 | m |
| Extra clearance | 1.00 | m |
| Wind speed | 25 | km/h |
| Slope percent | 8.0 | % |
| Workfront length | 30 | m |
| Output | Result | Unit |
|---|---|---|
| Recommended safety width | 13.86 | m |
| Exclusion diameter | 27.72 | m |
| Circular exclusion area | 603.32 | m² |
| Strip area (both sides) | 831.48 | m² |
Notes and limits
- This tool is for planning; verify with competent supervision.
- Increase exclusion distances for overhead lifting and public areas.
- Local regulations and project specs may require larger cordons.
- Wind and slope models here are simplified for quick estimates.
Safety area width planning note
1) Why safety area width matters
Safety width is the minimum offset that keeps people and equipment outside a predictable hazard envelope. On active sites, hazards come from swing radius, falling loads, flying debris, and moving plant. A defined width supports permit controls, access routes, and daily briefings, and it helps supervisors place barriers and signage consistently.
2) Inputs that drive the exclusion boundary
The estimate combines a hazard reach radius (R) with practical clearances. Activity presets apply a base clearance, such as 2.0 m for lifting, 1.5 m for excavation, and 3.0 m for demolition. Extra clearance accounts for walkways, spotters, or temporary protection. Wind adds a simple allowance using wind speed and a factor typically between 0.02 and 0.08 m per km/h.
3) Risk and slope adjustments
Risk multipliers expand the boundary to reflect uncertainty and exposure: 1.00 (low), 1.15 (medium), 1.30 (high), and 1.50 (extreme). Slope can increase roll‑out or slide distance. The slope factor uses 1 + (slope% × sensitivity); a sensitivity of 0.005 means a 10% slope increases width by about 5%.
4) Interpreting outputs for layout
The calculator returns a safety width, an equivalent exclusion diameter, and an estimated circular area. For linear work, it also estimates strip area for one side or both sides along a workfront length. Use the width to set barricade offsets, then confirm line‑of‑sight, emergency access, and exclusion signage positions.
5) Worked example snapshot
With R = 6.0 m, lifting preset (2.0 m), extra clearance 1.0 m, wind 25 km/h at 0.05, slope 8% at 0.005, and high risk (1.30), the recommended width is about 13.86 m. That corresponds to a 27.72 m diameter and roughly 603.60 m² circular area. For a 30 m workfront on both sides, strip area is about 831.48 m².
FAQs
1) What does “hazard reach radius” mean?
It is the maximum expected reach of the primary hazard, measured from its source. Examples include crane load swing, excavator bucket reach, or debris travel distance. Use the most conservative credible value from your plan.
2) When should I increase the risk level?
Increase risk when visibility is poor, multiple trades work nearby, public interfaces exist, or the hazard is hard to control. Higher multipliers add buffer for uncertainty and human factors during execution.
3) Why is wind included?
Wind can push suspended loads, dust, or sparks, and can reduce control near the hazard. The wind allowance provides a quick buffer. If you have a project wind limit, follow that limit first.
4) How do I use the strip area output?
Strip area estimates the cordon footprint along a linear workfront, such as trenching or a barrier line. Choose one side or both sides, enter workfront length, and use the area for layout and access planning.
5) Should I use meters or feet?
Use the unit system that matches your drawings and site measurements. The calculator converts outputs consistently. Wind remains in km/h for clarity; treat it as an input separate from distance units.
6) Is this a compliance tool?
No. It is a planning aid to support discussions, briefings, and layout checks. Always verify against local regulations, client specifications, method statements, and competent supervision before implementation.
7) What if I have multiple hazards?
Calculate for each significant hazard, then adopt the largest resulting width or define separate zones. Overlapping zones should use the more restrictive boundary, with clear signage and controlled access points.