Copper Pipe Size & Weight Converter
Convert copper pipe and tube sizes from inches and fractions to actual outside diameter (OD) in millimetres — plus a weight calculator for kg/m, lb/ft and total coil weight.
Copper Pipe Size to MM Conversion Chart
Actual outside diameter for the fractional-inch sizes most commonly seen on copper tube and line-set spec sheets, calculated as size (inches) × 25.4.
| Nominal size | Decimal (in) | Actual OD (mm) |
|---|---|---|
| 1/4″ | 0.250″ | 6.35 mm |
| 3/8″ | 0.375″ | 9.53 mm |
| 1/2″ | 0.500″ | 12.70 mm |
| 5/8″ | 0.625″ | 15.88 mm |
| 3/4″ | 0.750″ | 19.05 mm |
| 7/8″ | 0.875″ | 22.23 mm |
| 1″ | 1.000″ | 25.40 mm |
| 1-1/8″ | 1.125″ | 28.58 mm |
| 1-1/4″ | 1.250″ | 31.75 mm |
| 1-3/8″ | 1.375″ | 34.93 mm |
| 1-1/2″ | 1.500″ | 38.10 mm |
| 1-5/8″ | 1.625″ | 41.28 mm |
| 1-3/4″ | 1.750″ | 44.45 mm |
| 2″ | 2.000″ | 50.80 mm |
Nominal size vs. actual OD — read this before ordering fittings
Nominal copper tube size and the actual outside diameter can differ depending on the copper tube standard and application. ACR (air-conditioning and refrigeration) tube, the type used in most line sets, is sized by its literal outside diameter — so a 1/2″ ACR tube genuinely measures 12.70 mm across, exactly as this chart shows.
ASTM B88 plumbing tube (Types K, L and M) works differently: its nominal size is a trade designation that sits 1/8″ (3.175 mm) below the actual OD. A "1/2″" B88 tube therefore has a true outside diameter of 5/8″ (15.88 mm). The values above are actual OD conversions — always confirm which standard your drawing or spec references before cutting fittings or ferrules to size.
Copper Pipe OD Calculator — Type a Fraction to Convert
Type a fraction exactly as it's marked on the tube — 1/2, 5/8, 3/4, 1-1/8 — and the calculator converts it to actual OD in millimetres instantly. No need to work out the decimal yourself first.
Accepts simple fractions (1/2, 5/8), mixed numbers (1-1/8 or 1 1/8) and decimals (0.625).
How to Convert Inches to MM
One factor covers every copper pipe size: 1 inch equals 25.4 millimetres exactly, by international definition.
-
1
Confirm the OD in inches
Read the nominal size off the tube, coil label or spec sheet — for example
3/4″or1-1/8″. -
2
Turn the fraction into a decimal
Divide the fraction's top number by its bottom number, then add any whole-inch part.
3/4″ = 0.75″,1-1/8″ = 1 + 0.125 = 1.125″. -
3
Multiply by 25.4
Apply the formula
OD (mm) = OD (in) × 25.4. For 0.75″:0.75 × 25.4 = 19.05 mm. -
4
Round to a practical precision
Two decimal places (e.g.
19.05 mm) is standard for tube OD specs; round further only if your drawing calls for it. -
5
Check the tube standard
Verify whether the size is an ACR actual-OD size or an ASTM B88 nominal size before ordering fittings — see the note above.
Copper Pipe Weight Calculator — KG per Metre & LB per Foot
Pipe weight depends on both the outside diameter and the wall thickness. Enter both — wall thickness can be typed in mm or picked by gauge (SWG) — to get weight per metre and per foot instantly, based on copper's density of 8.96 g/cm³. Add a pipe length in mm, metres or feet to also get the total coil weight in kg.
Not sure of the OD in mm? Use the OD converter above to find it first.
How the weight is calculated
-
1
Get the OD and wall thickness in mm
Use the OD calculator above (or the size chart) if you only have the fraction size, and read the wall thickness off the coil marking or spec sheet.
-
2
Find the cross-sectional metal area
Area = π × WT × (OD − WT), in mm². This is the ring of copper metal in the pipe wall.
-
3
Multiply by copper's density
Weight (kg/m) = Area × 0.00896, using copper's density of about 8.96 g/cm³.
-
4
Scale to your pipe length
Multiply kg/m by the pipe length in metres to get total weight — the calculator does this automatically if you enter a length.
Wall thickness varies by tube type — always confirm before ordering
The same nominal OD can be supplied with different wall thicknesses depending on the tube type (ACR, Type K, L or M) and pressure rating, and weight scales directly with wall thickness. Use the actual wall thickness from your spec sheet or coil marking for an accurate figure — the calculator will not assume one for you.
Fraction to MM Conversion Examples
The same formula applied to a few of the most-searched copper pipe sizes.
Copper Tube Size FAQ
What is the actual OD of a 1/2 inch copper pipe in mm?
A 1/2″ ACR (air-conditioning and refrigeration) copper line, which is sized by its true outside diameter, measures 12.70 mm OD. A 1/2″ ASTM B88 plumbing tube (Types K, L, M) is a nominal size, and its actual OD is 5/8″ (15.88 mm).
How do you convert copper pipe size from inches to mm?
Multiply the outside diameter in inches by 25.4. For example, a 3/4″ OD converts to 0.75 × 25.4 = 19.05 mm. Convert any fraction to its decimal inch value first, then apply the factor.
Is copper pipe size the same as its actual outside diameter?
Not always. ACR/refrigeration tube is sized by actual OD, so the nominal size equals the true outside diameter. ASTM B88 plumbing tube uses a nominal size that sits 1/8″ smaller than the actual OD, so always confirm which standard applies before ordering fittings.
What is the OD of 3/4 inch copper pipe?
A 3/4″ ACR copper tube has an actual OD of 19.05 mm. A 3/4″ nominal ASTM B88 plumbing tube has an actual OD of 7/8″ (22.23 mm).
How many mm is 1 inch of copper pipe?
1 inch equals 25.40 mm exactly. This is the base conversion factor used for every size on this page: OD (mm) = OD (inches) × 25.4.
Why does nominal copper tube size differ from the actual OD?
Plumbing tube standards such as ASTM B88 historically sized tube by an internal reference diameter, so the marked nominal size sits 1/8″ below the true outside diameter. ACR and refrigeration tube standards size the tube by its literal outside diameter instead, so no offset applies.
Can I type a fraction like 1/2 directly into the calculator?
Yes. Type the fraction exactly as it appears on the tube — 1/2, 5/8, 3/4 — or a mixed number such as 1-1/8, and the calculator converts it to actual OD in millimetres instantly. Decimal values (e.g. 0.625) work too.
Can I use this calculator for copper tube fittings?
Yes — the calculator gives you the actual OD in mm, which is the dimension fitting manufacturers use to size sleeves, ferrules and compression joints. Always verify against the specific tube standard (ACR or ASTM B88) before ordering fittings.
How do you calculate the weight of a copper pipe?
Weight per metre (kg/m) = π × wall thickness × (OD − wall thickness) × 0.00896, using copper's density of about 8.96 g/cm³. Both OD and wall thickness should be in millimetres — use the weight calculator above to skip the maths.
What is the weight of 15mm copper pipe per metre?
A 15mm OD copper tube with a 1.0mm wall thickness weighs approximately 0.39 kg per metre, about 0.26 lb per foot. Actual weight varies slightly with the exact wall thickness supplied.
Does copper pipe weight depend on wall thickness?
Yes. Two tubes with the same outside diameter can have noticeably different weights if their wall thickness differs, since weight scales directly with wall thickness. Always use the wall thickness from your spec sheet or coil marking, not just the OD, for an accurate weight estimate.
How do I calculate the total weight of a length of copper pipe in mm or metres?
First calculate the weight per metre from the OD and wall thickness, then multiply by the pipe length in metres. If the length is given in millimetres, divide by 1000 first to convert it to metres. For example, 0.394 kg/m × 6 metres ≈ 2.36 kg. The weight calculator above does this for you automatically for a length in mm, metres or feet.
Who makes this copper pipe size and weight calculator?
This free calculator is built and maintained by MKB Copper Components, a manufacturer and exporter of copper tubes and precision copper components for HVAC and refrigeration applications based in Greater Noida, India.
Need copper tube cut and coiled to these exact sizes?
MKB manufactures LWC, straight-length and pancake-coil copper tube from Ø4.75 mm to Ø54 mm, exported to OEMs and distributors worldwide.