Fast fire-flow planning for designers, engineers, and site teams everywhere today easily. Model ISO-style demand, apply sprinkler reductions, and export results for reports quickly.
| Example | Length | Width | Stories | Construction | Occupancy | (X+P) | Sprinklers | Final Flow |
|---|---|---|---|---|---|---|---|---|
| Sample | 60 | 40 | 2 | Wood Frame (Class 1) | Ordinary (O=1.00) | 0.00 | No | ≈ 2,750 gpm |
| Sprinklered | 60 | 40 | 2 | Noncombustible (Class 3) | Ordinary (O=1.00) | 0.10 | Yes (75% min 1,000) | ≈ 1,000 gpm |
This calculator follows an ISO-style needed fire flow approach:
Ai is the fire flow area (area per floor × stories). F depends on construction type, Oi depends on occupancy, and (X + P)i reflects exposure and communication hazards.
If sprinklers are present, an optional editable reduction and minimum are applied after the base calculation.
Fire flow demand is the minimum water supply rate needed to support effective firefighting at a building. During design and construction, estimating demand helps teams size water mains, evaluate hydrant spacing, confirm pump capacity, and document expectations from the local authority. A practical estimate combines building size with factors representing construction combustibility, occupancy hazards, and exposures to nearby structures. The goal is a defensible planning number that can be refined as the project develops.
This calculator uses an ISO-style approach where the construction factor Ci rises with the square root of the effective fire flow area Ai. Larger footprints and more stories generally increase water demand because fire can involve more fuel and a wider attack perimeter. Occupancy intensity is represented through an occupancy factor, and exposure/communication values reflect spread risk from nearby buildings, openings, or connected spaces.
After you estimate demand, compare it to the available water supply. Hydrant tests typically report static pressure, residual pressure, and measured flow. Use those values, along with pipe lengths and elevations, to judge whether the system can support the target flow at acceptable residual pressure. If supply is short, options include adding a fire pump, upsizing mains, improving looping, using multiple hydrants, or providing on-site storage. During construction, temporary water arrangements should be reviewed because site changes and partial commissioning can reduce reliability.
Sprinklers can reduce expected fire flow in many adopted standards. Because rules vary, the reduction percentage and minimum allowable flow are editable. Use conservative values when guidance is unclear, and avoid reducing below a practical operational minimum. Rounding and min/max clamping are included to match how many agencies publish required fire flow in steps. The duration field estimates total volume for sustained operations, helpful when checking tanks or fire water reservoirs. For planning, run a few scenarios (different occupancies or exposure assumptions) and keep notes on why each factor was chosen. Clear documentation speeds review meetings and reduces redesign risk.
Example: A two‑story building, 60 by 40, wood frame, ordinary occupancy, and no exposure factors yields about 2,750 gpm after rounding. If sprinklers are present and you apply a 75% reduction with a 1,000 gpm minimum, the final demand becomes 1,000 gpm (minimum governs). Use results to compare against hydrants, tanks, or pumps, then confirm the final requirement with the local fire code official and water utility.
Fire flow is the water rate, in gallons per minute, needed to support hose streams and firefighting tactics for a structure fire at a specific site.
Use the effective fire flow area covered by the building footprint times the number of stories included by your method. When unsure, use total building floor area as a conservative start.
They represent exposure and communication risks, such as nearby buildings, openings, and connected spaces that can increase spread potential. If you do not have values, leave them at zero and document assumptions.
Often yes, but the allowed reduction and minimums depend on adopted codes and the authority having jurisdiction. Use the editable controls to match your local guidance.
Many agencies specify required fire flow in standard increments. Rounding helps align estimates with typical published requirements and simplifies comparison with hydrant and pump capacities.
gpm is commonly used for fire flow. You may also need total gallons for storage sizing, which this calculator provides using duration. Convert units only if your jurisdiction requires it.
No. Use it for planning, budgeting, and early design checks. Always confirm the final required fire flow with the local fire authority and water utility for your project address.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.