Pipe Volume, Pool & Tank Gallons, Water Flow Rate (GPM) & HVAC CFM Calculator

Compute rectangular and round pool/tank gallons, water weight, pipe volume & GPM flow rate, and HVAC CFM.

Rectangular Tank / Pool Volume & Pipe Flow Rate
10,772 US Gal (49 GPM)
Cylindrical Eq. (24' Dia): 16,921 gal • Water Weight: 89,896 lbs • HVAC: 144 CFM
Rectangular Volume (Gal / L) 10,772 gal (40,776 L)
Round Tank/Pool (24' Dia) 16,921 US gal
2" Pipe Volume & Flow 16.32 gal • 49 GPM
HVAC Airflow (6 ACH) 144 CFM
Inputs
ft
Length of rectangular pool/tank, or diameter of round pool/cylindrical tank.
ft
Width in feet for rectangular pools, tanks, or rooms.
ft
Average depth = (Shallow End + Deep End) ÷ 2.
in
Internal pipe diameter in inches (e.g., 3/4", 1", 1.5", 2", 4").
ft
Total linear pipe length to compute standing pipe volume.
ft/s
Residential copper/PEX supply lines typically design for 4–8 ft/s.
ACH
Living areas ≈ 4–6 ACH; bathrooms/kitchens/workshops ≈ 8–12 ACH.
Results & Graph
Rectangular Tank / Pool Volume & Pipe Flow Rate
10,772 US Gal (49 GPM)
Cylindrical Eq. (24' Dia): 16,921 gal • Water Weight: 89,896 lbs • HVAC: 144 CFM
Rectangular Volume (Gal / L)
10,772 gal (40,776 L)
Water Weight: 89,896 lbs
Round Tank/Pool (24' Dia)
16,921 US gal
2" Pipe Volume & Flow
16.32 gal • 49 GPM
Fills tank in 3.7 hrs
HVAC Airflow (6 ACH)
144 CFM
For 1,440 ft³ space

Pool/Tank Cross-Section, Pipe GPM Flow Curve & HVAC ACH Suite

Rectangular Gallons, Round Cylinder Gallons, and Filled Water Weight (lbs)
Graph 1 • Tank / Swimming Pool Cross-Section & Water Mass 1 ft³ = 7.48052 US gallons @ 8.345 lbs/gal
Length = 24 ft × Width = 12 ft Depth 5 ft 10,772 US Gallons (40,776 Liters • 1,440 ft³) Water Weight = 89,897 lbs (44.9 US Tons) Hydraulic Capacity Summary • Rectangular Pool/Tank: 10,772 gal • Round Tank (24' Dia): 16,921 gal • Fill Time @ 49.0 GPM: 3.7 hrs
Graph 2 • 2" Pipe Flow Rate (GPM) vs. Fluid Velocity (ft/s) IPC recommends 4–8 ft/s to prevent pipe erosion and water hammer
0 GPM 52.9 GPM 105.7 GPM 8 ft/s Max Safe Velocity Limit 2 ft/s: 19.6 GPM 19.6 2 ft/s 4 ft/s: 39.2 GPM 39.2 4 ft/s 5 ft/s: 49 GPM 49 5 ft/s 6 ft/s: 58.8 GPM 58.8 6 ft/s 8 ft/s: 78.3 GPM 78.3 8 ft/s 10 ft/s: 97.9 GPM 97.9 10 ft/s
Graph 3 • Room Ventilation Air Changes per Hour (ACH) vs. CFM CFM = (Room Cubic Feet × ACH) ÷ 60
0 CFM 155.5 CFM 311.0 CFM 2 ACH: 48 CFM 48 2 ACH 4 ACH: 96 CFM 96 4 ACH 6 ACH: 144 CFM 144 6 ACH 8 ACH: 192 CFM 192 8 ACH 10 ACH: 240 CFM 240 10 ACH 12 ACH: 288 CFM 288 12 ACH
Summary: Rectangular capacity is 10,772 gallons (89,896 lbs) and 2" pipe flow is 49 GPM.
Summary: A rectangular pool or tank measuring 24 ft × 12 ft × 5 ft holds 1,440 ft³ (10,772 US gallons or 40,776 liters) of water weighing 89,896 lbs (a round tank of 24 ft diameter holds 16,921 gallons). A 2-inch pipe running 100 ft contains 16.32 gallons of standing water and delivers 49 GPM at 5 ft/s velocity. For HVAC ventilation at 6 air changes per hour, required airflow is 144 CFM.

Formula & Mathematical Methodology: Hydraulic Capacity, Continuity Flow Rate (GPM) & ASHRAE CFM Equations

Gallonsrect = L × W × D × 7.48052,   GPM = 2.448 × din2 × vfps,   CFM = Volume (ft³) × ACH60
Gal_rect = L × W × D × 7.48052; GPM = 2.448 × d_in² × v_fps; CFM = (Volume_ft³ × ACH) / 60
  • 7.48052: Exact US liquid gallons per cubic foot (1,728 in³ ÷ 231 in³/gal)
  • din, v_fps: Pipe inside diameter in inches and fluid velocity in feet per second

Rounding: Pool and tank capacities round to nearest whole gallon/liter; pipe flow rounds to 1 decimal place.

Worked Example: 24' × 12' Pool with 5' Average Depth + 2" Pipe @ 5 ft/s

Find the volume, water weight, and fill time of a 24 × 12 × 5 ft pool supplied by a 2-inch pipe flowing at 5 ft/s.

  1. Pool volume = 1,440 ft³ × 7.48052 = 10,772 US gallons (40,776 L), weighing 89,896 lbs.
  2. 2" pipe standing volume = 0.0408 × 2² × 100 = 16.32 gallons.
  3. Pipe flow rate = 2.448 × 2² × 5 = 49.0 GPM, filling the 10,772-gallon pool in 3.7 hours.
Result: 10,772 US gallons (89,896 lbs) and 49.0 GPM flow rate.

Frequently Asked Questions

How many gallons are in 1 cubic foot of water?

There are 7.48052 US liquid gallons (or 28.3168 liters) in 1 cubic foot of water, weighing 62.43 pounds.

Why should residential plumbing water velocity stay below 5 to 8 feet per second?

Exceeding 8 ft/s (or 5 ft/s in hot water copper/PEX lines) causes pipe erosion-corrosion, whistling flow noise, and destructive water hammer pressure surges when valves close.

Construction & Home • Plumbing, Pools, Tanks & HVAC Guide

How to Use the Pipe Volume, Pool & Tank Gallons, Water Flow Rate (GPM) & HVAC CFM Calculator: Practical Guide & Visual Analysis

Size swimming pools, water storage tanks, plumbing lines, and ventilation fans in one place: convert cubic feet into US gallons, liters, and filled water weight (8.345 lb/gal), determine pipe volume and GPM flow from inner diameter and velocity, and calculate room CFM from Air Changes per Hour (ACH). Whether you are researching pool volume calculator, tank volume calculator, pipe volume calculator, water flow rate gpm calculator, cfm airflow calculator, this interactive tool helps you calculate swimming pool, cistern, or storage tank capacity in US gallons and liters, total water weight in pounds, plumbing pipe internal volume and GPM flow rate, and room HVAC CFM ventilation airflow.

Interpreting the 3 Custom Visual Graphs & Key Outputs

As you adjust Pool / Tank Length or Round Diameter (Feet), Rectangular Pool / Tank Width (Feet), Average Water Depth / Room Height (Feet), Plumbing Pipe Inner Diameter (Inches), the calculator immediately computes Rectangular & Cylindrical Tank / Pool Capacity (US Gallons & Liters), Filled Water Weight (lbs @ 8.345 lb/gal), Pipe Internal Volume (Gallons) & Volumetric Flow Rate (GPM), Required HVAC / Exhaust Fan Airflow (CFM) and updates all three domain-specific SVG charts in real time. Instead of relying on a single static figure, you can inspect the primary domain diagram, component breakdown, and multi-point trajectory curve to see how changing your inputs shifts the final result. Use the Compare (up to 3 scenarios) button to evaluate side-by-side variations before making a decision.

Real-World Benchmark & Planning Tips (Global Hydraulic & ASHRAE Ventilation Standard)

In our benchmark scenario (24' × 12' Pool with 5' Average Depth + 2" Pipe @ 5 ft/s), 10,772 US gallons (89,896 lbs) and 49.0 GPM flow rate. Keep in mind that uses 1 US liquid gallon = 231 cubic inches and freshwater density of 8.3454 lb/gal at 60°F (15.6°C). For related calculations in Construction & Home, explore Roofing, Stair Stringer, Tile, Mulch/Gravel & HVAC BTU Calculator, Unit Conversion Calculator, Geometry Calculator (Right Triangle, Circle & Cylinder).