Calculate foam concentrate,
water ratio, application time, and
tank loads for Class A, Class B (AFFF / AR-AFFF), and CAFS operations.
NFPA 11-aligned.
4 Types
A, B, AR-AFFF, CAFS
NFPA 11
Application rates
GPM + ft²
Area planning
Free
No login
Quick Reference
Class A
0.1%–1%
AFFF (B)
1%–6%
AR-AFFF
3%–6%
CAFS
0.1%–0.5%
Foam Solution Calculator
Results update instantly. All calculations follow NFPA 11 guidelines.
Foam concentrate
—
Water needed
—
Application time
—
at selected GPM
Mix ratio
—
conc. : water
Full breakdown
Foam type—
Concentration—
Tank size—
Concentrate per tank—
Water per tank—
Flow rate—
Tank duration at flow rate—
Illustrative tank-volume comparison
Example solution volume—
Example tank loads—
Concentrate for example—
Tanks available—
Available volume / example volume—
Tank loads visual:
⚠️ Insufficient tanks on scene. Additional supply required.
Training/planning use only. Always follow department SOP/SOG
and consult current NFPA 11 and ERG for incident operations.
Editorial policy
Foam Types for Firefighters
Firefighting foam is classified by the fuel type it suppresses.
Class A foam is used on ordinary combustibles (wood, vegetation, structure fires).
Class B foam (AFFF and AR-AFFF) suppresses flammable and combustible liquid fires.
CAFS uses compressed air to produce a lightweight, adhesive foam for wildland and overhaul operations.
Wildland, structure knockdown & overhaul; Class A concentrate
Typical ratios:
0.1%, 0.3%, 0.5%
Training example rate: 0.04 GPM/ft²
Understanding Concentration Ratios
The concentration percentage tells you how much foam concentrate goes into each gallon of finished solution:
Concentration
Concentrate / 100 gal
Water / 100 gal
Typical use
0.1%
0.1 gal
99.9 gal
CAFS wet foam, wildland
0.3%
0.3 gal
99.7 gal
Class A structure, CAFS standard
1%
1 gal
99 gal
AFFF on hydrocarbon (low-ratio)
3%
3 gal
97 gal
AFFF/AR-AFFF standard
6%
6 gal
94 gal
Fixed systems, polar solvents
Formula: Concentrate (gal) = Tank size (gal) × (concentration ÷ 100).
For a 500-gal tank at 3%: 500 × 0.03 = 15 gallons concentrate, 485 gallons water.
Common Foam Calculation Examples
500-gal tank at 3% AFFF
Common Class B hydrocarbon setup.
500 × 0.03 = 15 gal concentrate
Water needed: 485 gal
At 100 GPM: 5 minutes application time
750-gal tank at 0.3% Class A
Typical structure, overhaul, or WUI planning ratio.
750 × 0.003 = 2.25 gal concentrate
Water needed: 747.75 gal
At 150 GPM: 5 minutes application time
400 ft² spill at 0.10 GPM/ft²
Example Class B spill-fire planning estimate.
Required flow: 40 GPM
10-minute application: 400 gal solution
At 3%: 12 gal concentrate
These examples are for training and pre-incident planning. Confirm foam type, application rate, and duration with your department SOP/SOG and current product data sheet.
Application-Rate Examples and Product Listings
The values below are illustrative training inputs, not verified NFPA 11 minima or certified CAFS equivalencies. Actual rates and duration depend on the exact agent listing, fuel, application equipment and method. Do not use the area-based example as a fireground flow requirement or system design.
Foam type
Illustrative rate
Application method
Notes
Class A
0.05–0.10 GPM/ft²
Aspirated or CAFS
Varies by fuel depth and exposure
AFFF (Class B)
0.10 GPM/ft²
Aspirated or non-aspirated
Hydrocarbon example; verify the actual concentrate listing
AR-AFFF on hydrocarbons
0.10 GPM/ft²
Aspirated
Same rate as AFFF
AR-AFFF on polar solvents
0.10 GPM/ft²
Aspirated only
6% concentration required for polar solvents
CAFS training example
≈ 0.04 GPM/ft²
Compressed air
Illustrative input only; no certified equivalence is established
Always verify with current NFPA 11 and your department SOP.
Application rates for fixed systems, subsurface injection, and high-expansion foam differ significantly.
How to Use This Foam Calculator
1
Select foam type
Choose Class A, AFFF, AR-AFFF, or CAFS. Illustrative rate and concentration options update; they do not establish the correct agent or rate for an incident.
2
Choose concentration ratio
Select from the pre-set pills (e.g. 3% for AFFF) or enter a custom percentage. Your department SOP or the foam manufacturer's datasheet will specify the correct ratio for your foam.
3
Enter tank size and flow rate
Enter your apparatus tank capacity in gallons and your nozzle or master stream flow rate in GPM. The calculator instantly shows concentrate amount, water needed, and application time.
4
Add fire area for tank planning
Enter the estimated fire or spill area in square feet to calculate total solution required, tank loads needed, and whether your on-scene resources are sufficient.
5
Set available tanks
Enter the number of tank loads available (pre-fill, tender, etc.) to see coverage vs. demand and get an immediate gap warning if supply is insufficient.
CAFS Operations — What's Different
Compressed Air Foam Systems (CAFS) inject compressed air into a Class A foam solution before it leaves the pump, creating a very stable, lightweight foam blanket.
CAFS advantages
Dramatically reduces water use — effective at 0.1–0.5% concentrate
Foam sticks to vertical surfaces for exposure protection
Extended tank life — same tank covers more area
Lighter hose loads (air replaces water volume)
Excellent for wildland-urban interface and overhaul
CAFS limitations
Never use CAFS on Class B fires — not rated for flammable liquids
Requires properly calibrated CAFS system
Consistency depends on air-to-solution ratio (wet/dry foam)
Not all nozzles are CAFS-compatible
Special training required per department SOP
Foam Calculator FAQ
Foam concentrate (gallons) = Tank size (gallons) × (concentration% ÷ 100). For a 500-gallon tank at 3%: 500 × 0.03 = 15 gallons of concentrate and 485 gallons of water. Use the calculator above to instantly compute any combination.
AFFF (Aqueous Film-Forming Foam) is designed for hydrocarbon fuels like gasoline, diesel, and jet fuel. AR-AFFF (Alcohol-Resistant AFFF) works on both hydrocarbons AND polar solvents like ethanol, methanol, acetone, and other water-miscible fuels. If you face a polar solvent fire with regular AFFF, the foam breaks down immediately — identify the fuel and verify a specifically listed compatible concentrate and application method. Do not assume AR-AFFF is suitable for every unknown or mixed fuel; listed alcohol-resistant fluorine-free products also exist.
Use the listed concentrate instructions for the actual fuel, application method, equipment, concentration and duration. Generic NFPA examples are not a substitute for the product listing or an engineered design.
There is no universal rate covering every concentrate, fuel and delivery system. Use the exact product listing, manufacturer instructions, applicable adopted NFPA 11 requirements and department plan. Rates in this tool are illustrative training inputs, not verified minima or certified CAFS equivalencies.
Total solution needed (gal) = Fire area (ft²) × Application rate (GPM/ft²) × Application time (min). Tank loads = Total solution ÷ Apparatus tank size. Enter your fire area into the calculator above and it computes this automatically, including a warning if your available tanks are insufficient.
Application time (minutes) = Tank size (gallons) ÷ Flow rate (GPM). A 500-gallon tank at 100 GPM lasts 5 minutes. At 50 GPM, it lasts 10 minutes. Enter your flow rate in the calculator to see duration. For extended operations, plan tanker shuttle or hydrant supply before tank runs dry.
No. This tool is designed for mobile apparatus and fireground planning only. Fixed suppression system design (hangar systems, loading rack systems, tank farms) requires a licensed fire protection engineer and full compliance with NFPA 11, NFPA 30, and relevant codes. Do not use this tool for system design or acceptance testing.
Disclaimer: This calculator is for training and pre-incident planning only.
For live incidents, always follow your department SOP/SOG and consult the current
NFPA 11
and product manufacturer's datasheet.
Editorial policy ·
Our authors
⚠️ Disclaimer: This tool is for training and planning purposes only. Do not rely on these calculations as the sole basis for live fireground operations. Always defer to your department's SOPs. Read full operational disclaimer.
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