Fire protection · Assessed coverage only
Plan extinguisher quantities using assessed coverage inputs
Estimate quantities across identical zones using a coverage value supplied by your fire assessor.
By HSECalc · Published
Check that this method fits your task
An area arithmetic planner, not a fire-code sizing tool. There is no built-in universal coverage value. It does not determine extinguisher types, ratings or locations.
Choose your inputs and work through the steps
- Ask the responsible fire assessor for coverage appropriate to the selected equipment, hazards and local requirements. There is no universal area-per-unit input in this planner.
- Enter one zone’s area, the assessed coverage per unit and the number of identical zones. Use separate calculations for different zones.
- Round each zone’s area requirement up, then total the units. Keep the assessor’s design and layout review with the estimate.
Units per zone = ceiling(area / assessed coverage). Total = units per zone × identical zones. Layout and travel distance may increase the final quantity.
A worked example
Illustrative values explain the tool; they are not prescribed inputs for your work.
- Fictional zone: 450 m² with assessor-entered coverage of 200 m² per unit.
- 450 ÷ 200 = 2.25, rounded up to 3 units per zone.
- Two identical zones require an arithmetic total of 6; the assessed layout may require more.
Read the result and decide what needs checking
Area arithmetic cannot determine extinguisher type, rating, location or a compliant legal minimum. Accessibility and travel arrangements can increase the final quantity.
Do not average separated zones to reduce the count. The sample coverage below is fictional and must not be adopted as a design rule.
Common questions
Is this the legal minimum?
No. Area alone cannot establish a compliant quantity. Hazard class, rating, access and travel distances affect the design.
Can I use it outside the US?
Only as arithmetic with locally assessed inputs. The linked OSHA travel rules apply to their US context, not worldwide.
What if zones have different sizes?
Calculate each zone separately and total the quantities. Do not average across barriers or separate zones.
References and scope notes
Use the current official guidance and the instructions for your actual equipment. HSECalc is independent; a reference is not an endorsement. Read how we use methods and sources or report a correction.