First Aider Staffing Calculator

Example data table

Formula used

This calculator uses a practical planning model built from four steps:

1. BasePerShift = ceil(Workers / Ratio), where Ratio depends on risk.
2. ZoneMinimum = Zones if zones are separated; otherwise 1.
3. PerShift = max(BasePerShift, ZoneMinimum) + RemoteExtras + Redundancy.
4. TrainedPool = ceil((PerShift × Shifts) × (1 + Absence%)).

Default ratios: Low 1/50, Medium 1/25, High 1/10 workers per first aider. RemoteExtras increases by 1 at 30, 60 minutes travel, plus remote selection.

How to use this calculator

• Enter the peak number of workers expected on site.
• Select risk level based on the most hazardous planned activities.
• Set zones to reflect how spread out crews are during work.
• Choose shifts per day and mark remote conditions if applicable.
• Add an absence buffer to size your training pool reliably.
• Click Calculate, then download a CSV or PDF for records.

Professional guidance article

1) Why first aider staffing matters on construction sites

Construction work combines moving plant, temporary works, manual handling, work at height, and frequent subcontractor turnover. Fast first-aid response reduces injury severity, limits downtime, and supports incident reporting. Staffing plans also improve supervisor confidence during high-risk tasks and after-hours operations, when access to external medical support is slower.

2) Using headcount correctly for peak exposure

Use the highest expected headcount on site, not the average. Peak exposure typically occurs during concrete pours, structural steel phases, or simultaneous trades. If your headcount swings by day, plan around the busiest period and review weekly so first-aid coverage remains proportional to the workforce actually at risk.

3) Risk-based ratios and what they represent

The calculator applies planning ratios by risk level: low (1 per 50), medium (1 per 25), and high (1 per 10). These ratios are operational benchmarks that help you size coverage for likely injury frequency and complexity. They do not replace jurisdiction rules, client requirements, or project-specific medical plans.

4) Zone coverage for large footprints

A site can be compliant on paper yet slow in practice if crews are spread out. Separated zones such as multiple floors, remote laydown yards, or linear roadworks benefit from at least one local responder per zone. This reduces response time and avoids pulling a single trained person away from critical activities.

5) Shifts, overtime, and fatigue considerations

Multi-shift work increases the total on-duty requirement because responders must be present each shift. Factor in overtime, fatigue, and rotation so the same individuals are not repeatedly assigned. A larger trained pool supports coverage during leave, training refreshers, and last-minute roster changes.

6) Remote access and travel time to medical help

Distance to clinics and ambulance access can turn minor injuries into major events. The tool adds coverage when the site is remote or travel time exceeds 30 or 60 minutes. Use this as a prompt to also review emergency communications, rescue plans, and vehicle routes for stretcher access.

7) Building a reliable training pool with absence buffers

Absence buffers (for example 10–15%) account for holidays, sickness, turnover, and refresher courses. The trained pool number helps you nominate enough people so the recommended on-duty count is still achieved after real-world availability losses. Re-check the buffer after major mobilizations or contractor changes.

8) Documentation, audits, and continuous improvement

Export the CSV and PDF to attach to your safety plan, induction packs, and weekly look-ahead meetings. Record who is trained, expiry dates, and coverage by zone and shift. After incidents, compare response times against zone layout and staffing assumptions, then adjust the risk selection, redundancy, or training pool for future phases.

FAQs

1) Does this calculator confirm legal compliance?

No. It provides planning guidance. Always verify local regulations, client standards, and project medical plans, then adjust ratios, zone rules, and staffing expectations to match documented requirements.

2) Should I use average or maximum headcount?

Use the maximum expected headcount during the busiest work period. Peak exposure drives first-aid demand, and planning to the maximum reduces the risk of under-coverage during high-activity phases.

3) What counts as a separate zone?

A zone is an area where response time is meaningfully affected, such as multiple floors, distant workfaces, or linear projects. If one responder cannot reach all crews quickly, treat areas as separate zones.

4) How do I choose the risk level?

Base it on the most hazardous activities planned: heavy lifting, work at height, hot works, live traffic, and plant movement increase risk. If unsure, choose the higher level and document your rationale.

5) Why add an absence buffer?

People take leave, get reassigned, or miss refreshers. The buffer helps ensure the planned on-duty count is still met after normal availability losses, especially on longer projects.

6) What is redundancy, and when should I use it?

Redundancy adds extra responders per shift for resilience. Consider it during peak activities, when multiple zones operate simultaneously, or when high-risk tasks could occupy a responder for extended periods.

7) How should I use the skill mix suggestion?

Use it to plan a blend of responders, such as basic coverage in each zone with advanced capability available on the shift. Align skills with hazards, equipment, and the travel time to external medical care.