Calculator inputs
Use coverage, confidence, and risk settings to estimate a practical sample plan.
Example data table
| Scenario | Area (m²) | Coverage (cm²) | Confidence (%) | Prevalence (%) | Zones | Risk | Per zone | Total samples |
|---|---|---|---|---|---|---|---|---|
| Cleanroom prep bay | 120 | 100 | 95.0 | 10.0 | 3 | High | 6900 | 20700 |
| Office refurbishment | 60 | 200 | 90.0 | 10.0 | 2 | Medium | 2157 | 4314 |
| Mechanical room | 35 | 100 | 95.0 | 20.0 | 1 | Critical | 8050 | 8050 |
| Warehouse aisle | 250 | 400 | 95.0 | 5.0 | 5 | Medium | 1797 | 8985 |
These examples use the same calculation engine as the form.
Formula used
- Area-based minimum: N_area = ceil(Area / Coverage_per_sample)
- Statistical detection minimum: N_stat = ceil( ln(1 − CL) / ln(1 − p) )
- Base samples: N_base = max(N_area, N_stat)
- Adjusted samples: N_adj = ceil(N_base × Risk × Access × Variability)
- Hotspot extras: N_hot = ceil(N_adj × Hotspot%)
- Zone balancing: Per_zone = ceil(max(Min, N_adj+N_hot) / Zones), total = Per_zone × Zones
This blends a coverage-driven plan with a detection-confidence safeguard, then applies practical multipliers for field constraints.
How to use this calculator
1) Describe the surface
Choose Length × Width or Total Area. Pick units that match your drawings.
2) Set sampling coverage
Enter your swab or wipe coverage. Use 100 cm² if unsure.
3) Choose confidence and prevalence
Higher confidence or lower prevalence increases the statistical minimum.
4) Add zones and multipliers
Use zones for stratified coverage. Risk and access tune the final count.
5) Calculate and export
Review totals and per‑zone counts. Download CSV or PDF for QA records and site sign‑off.