Basic Flow Calculator
Preliminary flow calculations for fire fighting systems.
Project & Input Data
Your project criterion: enter the value from your governing code, specification or approved supplier data. No standard value is assumed.
Your project criterion: enter the value from your governing code, specification or approved supplier data. No standard value is assumed.
Your project criterion: enter the value from your governing code, specification or approved supplier data. No standard value is assumed.
Engineering Assumptions
Preliminary decision support
- The design density, design area and hose-stream allowance are all values from the standard governing the project (e.g. NFPA 13) and are user-entered; no density/area table is assumed.
- A preliminary decision-support estimate: the result does not replace an approved design calculation or review by a competent authority.
- All percentages and inputs are user-defined; the calculation is purely arithmetic and assumes no particular code or specification.
Formula Summary
- Sprinkler flow (L/min) = density × design area
- Total flow (L/min) = sprinkler flow + hose-stream allowance
Results
Enter your data and press Calculate to see the results.
Engineering Insight
The design density and area used are entirely determined by the hazard classification in the applicable standard; they are never estimated generically.
Recommended Action
Refer this preliminary flow to a competent fire engineer for the full hydraulic calculation and formal approval.
Next step
This calculator is fully usable as it is. Professional adds saved projects, calculation history and PDF/Excel reports; Premium adds the integrated workflows and the BOQ generator.
Sprinkler demand is the starting point for pump and storage discussions. Enter the design density and design area taken from the standard governing your project, add the hose-stream allowance, and the calculator returns the sprinkler flow and the total demand in litres per minute.
Method and assumptions
- Sprinkler flow (L/min) = density × design area
- Total flow (L/min) = sprinkler flow + hose-stream allowance
- The design density, design area and hose-stream allowance are all values from the standard governing the project (e.g. NFPA 13) and are user-entered; no density/area table is assumed.
- A preliminary decision-support estimate: the result does not replace an approved design calculation or review by a competent authority.
- All percentages and inputs are user-defined; the calculation is purely arithmetic and assumes no particular code or specification.
Worked example
A design density of 6 L/min·m² over a 140 m² design area, with a 500 L/min hose-stream allowance — all three values taken by the user from the project's governing standard.
| Result | Value |
|---|---|
| Sprinkler flow | 840 L/min |
| Total flow (L/min) | 1,340 L/min |
| Total flow (L/s) | 22.33 L/s |
These figures are produced by the same calculator engine used on this page.
Frequently asked questions
- Does the tool know my hazard classification?
- No. Density, area and hose allowance are all user-entered. The engine contains no density/area table and infers nothing about occupancy or hazard.
- Is this a hydraulic calculation?
- No. It is the demand flow only. Pipe network hydraulics, pressure balancing and node-by-node analysis are separate work and are not performed here.
- What can I do with the result?
- Use it as the input flow for storage and pump sizing discussions — the Fire Water Tank and Fire Pump estimate tools take a duty flow of this kind.
- Can it replace an approved fire design?
- Never. Fire protection design must be produced and approved by a competent licensed fire engineer and accepted by the authority having jurisdiction.
Related calculators
- Pressure CalculatorFire Fighting
- Fire Water Tank EstimateFire Fighting
- Fire Pump EstimateFire Fighting
Next step
Free calculators are open to everyone. Project saving and PDF/Excel reports come with Professional, and integrated workflows with Premium.