NB/ISO 7243 Thermal Stress Calculator Template

The Thermal Stress Calculator template follows the NB/ISO 7243 standard to help you assess heat exposure in the workplace. It consists of three sheets: an Input sheet where you enter measured values such as black globe temperature (BG), dry bulb temperature (DB), wet bulb temperature (WB), and relative humidity; a Calculation sheet that automatically converts those readings into the Wet‑Bulb Globe Temperature (WBGT) index using the ISO formulas; and a Summary sheet that displays the WBGT result, the corresponding risk category (low, moderate, high, very high) and a colour‑coded heat‑stress chart. Drop‑down menus let you select the activity level (light, moderate, heavy) which adjusts the permissible exposure limits, and conditional formatting highlights any values that exceed safe thresholds.

This template is especially useful for safety officers, HR managers, and supervisors who need to monitor heat stress for employees working outdoors or in hot indoor environments. By automating the complex calculations required by the NB/ISO 7243 standard, it eliminates manual spreadsheet errors and speeds up the generation of compliance reports. The clear visual summary helps you quickly identify problem areas, plan work‑rest cycles, and document heat‑stress assessments for regulatory audits, ultimately protecting workers’ health and reducing the risk of heat‑related incidents.

Anyone responsible for occupational health and safety can benefit from this tool—whether you’re managing a construction crew, a manufacturing floor, or a field service team. The template tracks daily temperature readings, humidity levels, and activity classifications, producing a concise WBGT index that can be compared against industry‑approved limits. It also logs the date, location, and personnel involved, creating a historical record that supports trend analysis and continuous improvement of heat‑stress management policies.

How to use

1. Open the Input sheet and fill in the measured values for each shift: BH (black globe temperature), BC (dry bulb), GL (wet bulb), TGBHe, TGBHi, and relative humidity.
2. Choose the work‑load category from the drop‑down list (light, moderate, heavy) to let the template apply the correct exposure limits.
3. The Calculation sheet instantly updates the WBGT index and risk level; review the colour‑coded alerts on the Summary sheet.
4. Export the Summary sheet as a PDF or copy the results into your safety report to document compliance.

Expected benefits include a noticeable reduction in time spent on manual heat‑stress calculations and fewer errors in compliance reporting, allowing you to focus on proactive safety measures rather than tedious data entry.