Knowing how many gallons a pipe holds per linear foot is essential for plumbing, irrigation, chemical dosing, water treatment, and antifreeze calculations. This calculator handles any pipe diameter — from residential plumbing to industrial process piping — and provides results in US gallons and liters.
Last updated: June 2026 — Volume calculations based on inside pipe diameter (nominal ID) per ANSI/ASME B36.10 for steel pipe and ASTM D1785 for PVC Schedule 40.
Gallons Per Linear Foot Calculator
Use inside diameter (ID), not nominal pipe size
Gallons Per Linear Foot Chart — Standard Pipe Sizes
Volumes calculated using the inside diameter of Schedule 40 steel pipe. PVC and copper pipe have slightly different IDs — check manufacturer specs for exact dimensions. Typical residential and light commercial sizes:
| Nominal Size | Inside Diameter (in) | Gallons Per Foot | Gallons Per 100 ft | Liters Per Meter | Typical Application |
|---|---|---|---|---|---|
| 1/2" | 0.622 | 0.016 | 1.6 | 0.196 | Residential supply lines |
| 3/4" | 0.824 | 0.028 | 2.8 | 0.344 | Main supply, hose bibs |
| 1" | 1.049 | 0.045 | 4.5 | 0.558 | Main water line, pool plumbing |
| 1-1/4" | 1.380 | 0.078 | 7.8 | 0.965 | Well lines, irrigation main |
| 1-1/2" | 1.610 | 0.106 | 10.6 | 1.313 | Pool suction, irrigation zone |
| 2" | 2.067 | 0.174 | 17.4 | 2.164 | Main drain, sewer lateral |
| 3" | 3.068 | 0.384 | 38.4 | 4.767 | Sewer main, downspout drain |
| 4" | 4.026 | 0.661 | 66.1 | 8.206 | Building sewer, storm drain |
| 6" | 6.065 | 1.501 | 150.1 | 18.624 | Municipal sewer, fire main |
| 8" | 7.981 | 2.599 | 259.9 | 32.258 | Water main, large storm |
| 10" | 10.020 | 4.097 | 409.7 | 50.854 | Transmission main |
| 12" | 12.000 | 5.875 | 587.5 | 72.932 | Distribution main |
| 24" | 24.000 | 23.502 | 2,350 | 291.727 | Transmission trunk |
PVC Schedule 40 has a slightly larger inside diameter than steel pipe of the same nominal size. For precise chemical or dosing calculations, use the manufacturer's actual ID, not the nominal values above. A difference of 0.1 inches in ID on a 200-foot pipe run can change the total volume by several gallons.
How to Calculate Gallons Per Linear Foot — Formula & Examples
The fundamental formula converts the cross-sectional area of a pipe (in square inches) to gallons of volume per linear foot:
Where d is the inside diameter in inches, and 231 is the number of cubic inches in one US gallon.
Simplified Formula
Since π/4/231 = 0.0034, you can use the shortcut:
Example 1: 4-Inch Pipe
For a pipe with 4.026-inch inside diameter (Schedule 40 4" steel pipe): Gallons per foot = 4.026² × 0.0034 = 16.21 × 0.0034 = 0.661 gallons per foot. A 150-foot run holds 0.661 × 150 = 99.2 gallons.
Example 2: Antifreeze Calculation
A hydronic heating system has 300 linear feet of 1-inch copper pipe (ID = 1.025 inches). Volume = 1.025² × 0.0034 × 300 = 0.00357 × 300 = 1.07 gallons. This small volume explains why residential heating systems don't need large volumes of antifreeze — the pipe volume is surprisingly small.
Example 3: Irrigation Main Line
An irrigation system uses 500 feet of 2-inch Class 200 PVC pipe (ID = 2.149 inches). Volume = 2.149² × 0.0034 × 500 = 0.0157 × 500 = 7.85 gallons. When winterizing this system with compressed air, you need enough air volume to displace 7.85 gallons of water from the pipes.
Why Gallons Per Linear Foot Matters — Real-World Applications
Chemical Dosing & Water Treatment
When injecting chlorine, corrosion inhibitors, or pH adjusters into a water system, you must know the total pipe volume to calculate the correct dose. Overdosing a small pipe system by treating it like a large one wastes chemicals and can damage equipment. Underdosing fails to achieve treatment goals. The difference between a 4-inch pipe (0.66 gal/ft) and a 6-inch pipe (1.50 gal/ft) is more than 2× the volume — get it wrong and your chemical dose is off by 100%.
Winterization & Antifreeze
When blowing out irrigation systems or adding antifreeze to plumbing, knowing the total gallons in the pipe system tells you how much compressed air or antifreeze is needed. The common mistake is overestimating pipe volume — a 500-foot run of 1-inch pipe holds only 1.8 gallons, not the 10+ gallons people guess. For RV and boat winterization, accurate pipe volume prevents freeze damage: an RV fresh water system with 50 feet of 1/2-inch PEX holds approximately 0.8 gallons.
Fire Sprinkler System Design
Fire suppression systems must deliver a specific volume of water within a specific time to each sprinkler head. The pipe volume between the water source and the farthest head determines how long water takes to arrive after the valve opens. A 200-foot main of 4-inch pipe holds 132 gallons — at a flow rate of 100 GPM, it takes 1.3 minutes just to fill the pipe before water reaches the first sprinkler. This "water travel time" is a critical fire safety calculation.
Gravity Drainage & Sewer Design
Gravity sewer and storm drain pipes are designed to run partially full (typically 50–75% of diameter). The gallons-per-foot capacity at partial fill is different from the full-pipe value. At 50% fill, capacity is approximately 40% of the full-pipe volume, not 50% — because the cross-sectional area of a circle at half depth is 0.5 of the area minus the chord area. For drainage design, always use Manning's equation, not simple volume calculations.