Copper Pipe Volume Calculator
Same volume in every unit
Fluid weight
Estimated fill / drain time
Your recent calculations (saved on this device)
| When | ID | Length | Result |
|---|
Type L is preloaded (the common residential grade). Switch to K or M as needed.
How to use this calculator
- Choose the unit system — US, Imperial or metric — at the top of the calculator.
- Pick the pipe type and schedule, then the nominal size, and the real inside diameter loads for you. Or choose Custom and type any bore.
- Enter the pipe length. Open Advanced to set fill level, number of identical runs, a fittings allowance, the fluid, or a flow rate.
- Press Calculate to see the volume in every unit, plus fluid weight, cross-section area and fill or drain time.
- Copy, share or print the result. Recent calculations are saved on your own device so you can reopen them later.
Tip: not sure where to start? Use the Fill example data button to load a complete worked example — a 2-inch Schedule 40 line, 50 ft long, at 10 gal/min — then adjust the numbers to match your job.
Real-world uses, with numbers
Charging a radiant-heat loop
How much water sits in a 300 ft run of ½" PEX.
≈ 2.9 US galSizing a well pressure tank
Line-fill volume in 100 ft of 1" Schedule 40.
≈ 4.5 US galFlushing a main
Water to displace in 100 ft of 4" Schedule 40.
≈ 66 gal · 250 LWater weight on hangers
Load from a full 100 ft run of 2" pipe.
≈ 145 lb · 66 kgMetric heating fill
Charge volume for 50 m of 28 mm bore.
≈ 30.8 LFuel or oil line contents
Diesel held in 20 m of 50 mm bore.
≈ 39 L · 33 kgMore questions, answered
How do I convert between gallons, litres and cubic metres?
1 US gallon = 3.785 litres; 1 Imperial gallon = 4.546 litres; 1 m³ = 1,000 litres = 264.2 US gallons. The calculator shows all of them from a single entry, so you never convert by hand.
Does the pipe material change the volume?
Only through the bore. Two pipes with the same inside diameter hold the same volume whether they are steel, PVC, copper or PEX. Material and schedule matter because they set the real inside diameter for a given nominal size.
How much does the water inside a pipe weigh?
About 8.34 lb per US gallon, or 1 kg per litre. A full 100 ft run of 2" Schedule 40 holds roughly 17.4 gallons, about 145 lb. Set the fluid in Advanced for hot water, glycol, diesel or seawater.
What if I only know the outside diameter?
Switch the diameter to OD mode and enter the wall thickness; the tool subtracts two wall thicknesses to reach the bore. For a listed standard, just pick the size and the published inside diameter loads automatically.
Can I use it for a part-full or sloped drain?
Yes for a straight, round pipe: open Advanced and set the fill level below 100%, and the volume scales with it. Truly partial gravity flow in a sloped line follows a curved free surface, so treat the part-full figure as an approximation.
Notes and derived figures
- Volume scales with the square of the bore: doubling the inside diameter roughly quadruples the capacity, while doubling the length only doubles it.
- Per-foot and per-metre capacity are constant for a given bore, so any length is a single multiplication — handy for quick field estimates.
- Nominal size is a label. A "2-inch" Schedule 40 pipe has a 2.067-inch bore; using "2" overstates the volume by more than a third.
- Fill and drain time is volume divided by flow rate. Enter a flow rate in Advanced to turn any result into a charge, flush or drain time.
Type K, L and M — why the bore differs
Copper water tube comes in three common wall thicknesses. Type K is thickest (smallest bore), Type L is the general-purpose residential and commercial grade, and Type M is thinnest (largest bore). They share the same outside diameter for a given size, so the bore — and therefore the volume per foot — changes with type. A 1-inch Type K tube has a 0.995 in bore; Type M is 1.055 in. Choosing the wrong type quietly shifts your volume by a few percent.
| Nominal | Type K ID | Type L ID | Type M ID |
|---|---|---|---|
| 1/2" | 0.527" | 0.545" | 0.569" |
| 3/4" | 0.745" | 0.785" | 0.811" |
| 1" | 0.995" | 1.025" | 1.055" |
| 1-1/4" | 1.245" | 1.265" | 1.291" |
| 1-1/2" | 1.481" | 1.505" | 1.527" |
| 2" | 1.959" | 1.985" | 2.009" |
Copper's "nominal" size is smaller than the OD
Copper water tube follows an unusual rule: the actual outside diameter is 1/8 inch larger than the nominal size. A "3/4-inch" tube is really 0.875 in on the outside, with a Type L bore of 0.785 in. The calculator applies the correct bore automatically once you pick the type and size, so you do not have to remember the offset.
Common copper-volume jobs
- Hot-water recirculation loops — loop volume affects heat loss and pump sizing.
- Refrigerant and medical gas lines — internal volume matters for charge and purge.
- Radiant and baseboard heating — system water totals feed expansion-tank sizing.
- Repipes and estimates — knowing contents helps plan draining and refilling.
A worked copper example
A 40 ft loop of 3/4-inch Type L copper (bore 0.785 in) holds about 0.025 gallons per foot, so roughly 1.0 gallon of water — about 8.4 lb. On a recirculation loop that small volume turns over quickly, which is exactly why loop sizing and pump flow are linked. The calculator shows the volume, the weight, and the turnover time at your pump's flow rate.
Accuracy notes for copper
Match the type to your tube — most residential supply is Type L, while Type M is common where codes allow and Type K is used underground and for medical gas. If a system is scaled or lined, the effective bore is smaller than new. For non-standard or measured tube, Custom mode lets you enter the bore directly.
Reading and trusting your result
Here is how to read the number this copper pipe volume calculator gives you, and where it stops being exact.
What the figure represents
The headline value is the internal capacity of a round, uniform pipe running full — the fluid the bore can hold along the length you entered. Every other unit on the panel is the same physical quantity re-expressed, so you can quote whichever your paperwork needs without recalculating.
The full-pipe assumption
By default the figure assumes the pipe is completely full and perfectly cylindrical. For gravity drains and vented lines that run part full, set a fill level below 100% and the result scales with it. Bends, valves and fittings add a little capacity the straight-length model does not see — use the fittings allowance to approximate them.
Capacity reference tables & a worked example
Concrete numbers for this page, calculated the same way the tool above does — use them as a quick check or a lookup.
Type L copper 2" pipe: volume by run length
How much a 2" Type L copper bore holds as the run gets longer, in US gal. The per-foot figure is constant, so any length is one multiplication away.
| Length (ft) | Volume (US gal) | Per foot |
|---|---|---|
| 10 ft | 1.61 | 0.1608 |
| 25 ft | 4.02 | 0.1608 |
| 50 ft | 8.04 | 0.1608 |
| 100 ft | 16.08 | 0.1608 |
| 250 ft | 40.19 | 0.1608 |
| 500 ft | 80.38 | 0.1608 |
Type L copper pipe: volume across sizes
Volume held by a fixed 100 ft run across common Type L copper sizes, in US gal. Doubling the diameter roughly quadruples the capacity.
| Nominal size | Bore (in) | Volume in 100 ft (US gal) |
|---|---|---|
| 1/2" | 0.545 | 1.21 |
| 3/4" | 0.785 | 2.51 |
| 1" | 1.025 | 4.29 |
| 1-1/4" | 1.265 | 6.53 |
| 1-1/2" | 1.505 | 9.24 |
| 2" | 1.985 | 16.08 |
Worked example, step by step
- Bore = 1.985 in, so radius = 0.9925 in.
- Area = π × radius² = 3.0946 in².
- Length = 75 ft = 900 in; volume = 3.0946 × 900 = 2,785.2 in³.
- Convert to the unit you need: 12.06 US gal for a 75 ft run of Type L copper 2" pipe.
Frequently asked questions
How do I calculate water volume in a copper pipe?
Select the copper type (K, L or M) and size to load the bore, enter the length, and read the volume. The tool uses ASTM B88 inside diameters and V = π × (ID/2)² × L.
What is the difference between Type K, L and M copper for volume?
They share an outside diameter but have different wall thicknesses: K is thickest with the smallest bore, M is thinnest with the largest bore, and L sits in between. More bore means more volume per foot.
Why is copper tube bigger than its nominal size?
Copper water tube's outside diameter is 1/8 inch larger than the nominal size, so a 1/2-inch tube is actually 0.625 in on the outside. The calculator accounts for this.
Does this work for refrigeration (ACR) copper?
ACR tube is sized by actual OD rather than nominal, so measure the OD and wall and use Custom (OD mode) for the most accurate bore.
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What people say
The fill-time estimate turned a vague flush task into a scheduled one. Handy.
Clear about its own limits — tells you when to check manufacturer data. Trustworthy.
Clean and quick on my phone in the field.