Pipe Volume Calculator
Calculate pipe volume from standard US pipe sizes and materials. Get gallons, liters, cubic feet, water weight, and gallons per foot. Supports multiple pipes.
🔧 Pipe Volume Calculator
PIPE
VOLUME (per pipe)
💡 How to Calculate Pipe Volume
Pipe volume is the internal capacity of a pipe, typically calculated for plumbing, HVAC, fire sprinkler, and irrigation systems. Knowing the volume is essential for filling, draining, flushing, sizing expansion tanks, calculating antifreeze amounts, and estimating water weight.
The calculator above uses actual inner diameters for 8 standard US pipe sizes across 5 pipe materials, calculates water weight, and supports multi-pipe systems.
Calculate flow with our flow rate calculator. For tanks, see our tank volume calculator. Check velocity with our water velocity calculator.
Pipe Volume Formula
Volume = π × r² × L — or equivalently: Volume = π × (D/2)² × L
Where r = inner radius, D = inner diameter, L = length. All measurements must be in the same units.
For US gallons: Calculate volume in cubic inches, then divide by 231 (1 US gallon = 231 cubic inches).
Example: 1" copper pipe (1.049" ID) × 100 ft (1,200"):
V = π × (1.049/2)² × 1,200 = π × 0.275 × 1,200 = 1,037 cu in = 4.49 gal
Gallons Per Foot by Pipe Size
| Nominal Size | Copper (Type L) | PEX | PVC (Sch 40) | Gal/100 ft (Copper) |
|---|---|---|---|---|
| ½" | 0.0160 gal/ft | 0.0093 gal/ft | 0.0160 gal/ft | 1.60 |
| ¾" | 0.0280 gal/ft | 0.0191 gal/ft | 0.0280 gal/ft | 2.80 |
| 1" | 0.0449 gal/ft | 0.0304 gal/ft | 0.0449 gal/ft | 4.49 |
| 1¼" | 0.0764 gal/ft | 0.0496 gal/ft | 0.0778 gal/ft | 7.64 |
| 1½" | 0.1059 gal/ft | 0.0753 gal/ft | 0.1059 gal/ft | 10.59 |
| 2" | 0.1746 gal/ft | 0.1209 gal/ft | 0.1746 gal/ft | 17.46 |
| 3" | 0.3844 gal/ft | — | 0.3844 gal/ft | 38.44 |
| 4" | 0.6623 gal/ft | — | 0.6623 gal/ft | 66.23 |
Key insight: PEX pipes hold 30–40% less water than copper pipes of the same nominal size due to thicker walls and smaller ID.
Water Weight per 100 Feet
| Pipe Size (Copper) | Gallons/100 ft | Water Weight |
|---|---|---|
| ½" | 1.60 gal | 13.3 lbs |
| ¾" | 2.80 gal | 23.4 lbs |
| 1" | 4.49 gal | 37.4 lbs |
| 1½" | 10.59 gal | 88.3 lbs |
| 2" | 17.46 gal | 145.6 lbs |
| 3" | 38.44 gal | 320.6 lbs |
| 4" | 66.23 gal | 552.4 lbs |
Water weighs 8.34 lbs per gallon at 60°F. For hot water (140°F), weight decreases ~1% to 8.26 lbs/gal. For structural load calculations, use the higher cold-water weight.
Nominal Size vs. Actual Inner Diameter
Nominal pipe size is a trade designation — NOT the actual measurement. The actual ID varies significantly by material:
| Nominal | Copper L | PEX | CPVC | PVC Sch 40 |
|---|---|---|---|---|
| ½" | 0.622" | 0.475" | 0.536" | 0.622" |
| ¾" | 0.824" | 0.681" | 0.720" | 0.824" |
| 1" | 1.049" | 0.863" | 0.920" | 1.049" |
| 2" | 2.067" | 1.720" | 1.935" | 2.067" |
Always use actual ID for volume calculations. Using nominal size will give incorrect results — a "1-inch" PEX pipe holds 32% less water than a "1-inch" copper pipe.
Common Applications
- Drain-down volume: How much water you'll drain from a system (winterization, repair)
- Fill volume: How much water to add when filling a new system or after repairs
- Antifreeze calculation: Volume needed for glycol mix in radiant heating systems
- Expansion tank sizing: Total system volume determines expansion tank size
- Water hammer analysis: More water = more potential energy = worse water hammer
- Structural load: Water weight for floor/ceiling support calculations