Aluminium round tube is hollow cylindrical stock made by extrusion, cold drawing or seam welding, in alloys from 1100 to 7075. For most structural and general uses 6061-T6 or 6063-T5/T6 extruded tube is the right choice; seamless drawn tube is used where pressure, tight tolerance or a fine surface matters, and welded tube where low cost per metre counts. This guide explains how to choose between them, and gives size, weight and standards data for ordering.
Round tube looks like a simple product, but four choices determine whether it suits the job: the alloy and temper, the manufacturing route (seamless, porthole extruded, cold-drawn or welded), the outside diameter and wall thickness, and the standard that governs tolerance and testing. Most problems with tube, such as splits during bending, leaks under pressure or poor anodising, trace back to one of these choices rather than to the supplier.
Round tube is used across almost every industry: frames, handrails and furniture; hydraulic and pneumatic lines; heat-exchanger and HVAC tubing; masts, antenna and telescopic poles; bicycle, motorsport and aircraft structures; and conveyor rollers and machine guards. Its circular section gives equal stiffness in every direction and the best torsional stiffness per kilogram of any open or closed shape, which is why it is preferred for shafts, struts and members that twist.
For a short product specification of the tube Metline supplies, see the round tube specification page. Pipe in nominal pipe sizes and schedules is covered separately on the aluminium pipe page.
| Type | How it is made | Strengths | Limitations | Typical standards |
|---|---|---|---|---|
| Seamless extruded | Hollow or pierced billet extruded over a mandrel, so the wall has no joint | Uniform wall properties, suitable for pressure and critical service | Higher cost; thicker minimum walls than porthole | ASTM B241, EN 755-7 |
| Porthole (structural) extruded | Solid billet splits around the bridges of a porthole die and re-welds in the welding chamber | Lower cost, thin walls, long lengths; most structural tube | Longitudinal extrusion seam welds; not normally accepted for pressure duty | ASTM B221, B429, EN 755-8 |
| Cold-drawn seamless | Seamless extruded tube drawn over a plug or mandrel at room temperature | Tight tolerance, thin walls, fine surface, higher strength in H tempers | Smaller diameters; extra process cost | ASTM B210, B483, EN 754-7 |
| Welded | Strip roll-formed into a tube and seam-welded by high-frequency or TIG welding | Lowest cost per metre, very thin walls, coils for heat exchangers | Weld seam affects properties and appearance | ASTM B313, EN 1592 |
The distinction between seamless and porthole tube matters most. Porthole tube contains seam welds formed in the solid state as the metal rejoins inside the die. Modern practice makes those welds sound for structural use, and porthole tube is the bulk of tube sold for frames and furniture. Pressure-vessel codes and many aerospace specifications, however, require seamless tube. If a drawing says "seamless", order to ASTM B241, B210 or EN 755-7 and check that the certificate states it. More detail is in our guides to seamless tube, drawn tube and welded tube.
| Alloy and temper | Typical tensile strength | Typical yield strength | Character | Typical uses |
|---|---|---|---|---|
| 1100-H14 | 125 MPa | 115 MPa | Pure, very ductile, high conductivity | Ducting, chemical lines, signage |
| 3003-H14 | 150 MPa | 145 MPa | Formable, corrosion resistant | HVAC, heat exchangers, bent tube |
| 5052-H32 | 228 MPa | 193 MPa | Good strength, excellent corrosion resistance | Fuel and hydraulic lines, marine parts |
| 5083-O / H111 | 290 MPa | 145 MPa | High strength 5xxx, keeps properties when welded | Marine and offshore structures |
| 5086-H32 | 290 MPa | 207 MPa | Similar to 5083 with slightly better formability | Boat fittings, marine piping |
| 6063-T5 | 186 MPa | 145 MPa | Best surface and anodising response | Architecture, furniture, handrails |
| 6063-T6 | 241 MPa | 214 MPa | Stronger architectural grade | Railings, frames, light structures |
| 6061-T6 | 310 MPa | 276 MPa | All-round structural grade, weldable | Frames, masts, machine and vehicle parts |
| 6082-T6 (EN 755-2 min.) | 290 – 310 MPa min | 250 – 260 MPa min | European structural grade | Structures, trailers, scaffolding |
| 2024-T3 | 483 MPa | 345 MPa | High strength and fatigue resistance | Aircraft structures, fittings |
| 7075-T6 | 572 MPa | 503 MPa | Highest strength common tube | Aerospace, sports equipment, high-load struts |
Typical values from Aluminum Association and ASM data, except 6082 which shows EN 755-2 minimums, which depend on wall thickness. Tempers such as 6063-T832 (drawn and aged) and 7005 or 7020 (weldable Al-Zn-Mg tube for frames) are also available; their properties are reported on the mill certificate.
Two common mistakes: choosing 6063 for a load-bearing frame because it is the cheapest extruded tube, and choosing 7075 for a welded structure. 6063 has only about two thirds of the yield strength of 6061, and 7075 is not suitable for fusion welding. For welded high-strength frames, the Al-Zn-Mg alloys 7005 and 7020 are the usual answer because they recover much of their strength by natural ageing after welding.
The table lists commonly produced metric outside diameter × wall combinations. Weights are theoretical at 2.70 g/cm³; for 2024 and 7075 multiply by about 1.03 – 1.04. Standard lengths are usually 3 m, 5.8 m or 6 m, with cut lengths to order.
| OD × wall (mm) | ID (mm) | kg per metre | kg per 6 m length |
|---|---|---|---|
| 10 × 1 | 8 | 0.076 | 0.46 |
| 10 × 1.5 | 7 | 0.108 | 0.65 |
| 10 × 2 | 6 | 0.136 | 0.81 |
| 12 × 1 | 10 | 0.093 | 0.56 |
| 12 × 1.5 | 9 | 0.134 | 0.80 |
| 12 × 2 | 8 | 0.170 | 1.02 |
| 16 × 1 | 14 | 0.127 | 0.76 |
| 16 × 1.5 | 13 | 0.184 | 1.11 |
| 16 × 2 | 12 | 0.238 | 1.43 |
| 20 × 1 | 18 | 0.161 | 0.97 |
| 20 × 1.5 | 17 | 0.235 | 1.41 |
| 20 × 2 | 16 | 0.305 | 1.83 |
| 20 × 3 | 14 | 0.433 | 2.60 |
| 25 × 1.5 | 22 | 0.299 | 1.79 |
| 25 × 2 | 21 | 0.390 | 2.34 |
| 25 × 3 | 19 | 0.560 | 3.36 |
| 30 × 2 | 26 | 0.475 | 2.85 |
| 30 × 3 | 24 | 0.687 | 4.12 |
| 30 × 4 | 22 | 0.882 | 5.29 |
| 32 × 2 | 28 | 0.509 | 3.05 |
| 32 × 3 | 26 | 0.738 | 4.43 |
| 40 × 2 | 36 | 0.645 | 3.87 |
| 40 × 3 | 34 | 0.942 | 5.65 |
| 40 × 4 | 32 | 1.221 | 7.33 |
| 40 × 5 | 30 | 1.484 | 8.91 |
| 50 × 2 | 46 | 0.814 | 4.89 |
| 50 × 3 | 44 | 1.196 | 7.18 |
| 50 × 5 | 40 | 1.909 | 11.45 |
| 60 × 2 | 56 | 0.984 | 5.90 |
| 60 × 3 | 54 | 1.450 | 8.70 |
| 60 × 5 | 50 | 2.333 | 14.00 |
| 63 × 3 | 57 | 1.527 | 9.16 |
| 63 × 5 | 53 | 2.460 | 14.76 |
| 70 × 3 | 64 | 1.705 | 10.23 |
| 70 × 5 | 60 | 2.757 | 16.54 |
| 80 × 3 | 74 | 1.959 | 11.76 |
| 80 × 5 | 70 | 3.181 | 19.09 |
| 80 × 10 | 60 | 5.938 | 35.63 |
| 100 × 3 | 94 | 2.468 | 14.81 |
| 100 × 5 | 90 | 4.029 | 24.17 |
| 100 × 10 | 80 | 7.634 | 45.80 |
| 120 × 5 | 110 | 4.877 | 29.26 |
| 120 × 10 | 100 | 9.331 | 55.98 |
| 150 × 5 | 140 | 6.150 | 36.90 |
| 150 × 10 | 130 | 11.875 | 71.25 |
| 150 × 15 | 120 | 17.177 | 103.06 |
| 200 × 5 | 190 | 8.270 | 49.62 |
| 200 × 10 | 180 | 16.116 | 96.70 |
| 200 × 20 | 160 | 30.536 | 183.22 |
Size availability depends on alloy and route; very thin walls on large diameters are normally porthole or welded tube, while thick walls and small IDs are seamless.
Inch tube is ordered by outside diameter and wall in decimal inches. Wall thicknesses such as 0.035, 0.049, 0.065 and 0.083 in come from the traditional gauge series (20, 18, 16 and 14 gauge). Standard lengths are typically 12 ft or 20 ft.
| OD × wall (in) | Metric equivalent (mm) | lb per foot | kg per metre |
|---|---|---|---|
| 0.5 × 0.035 | 12.70 × 0.89 | 0.060 | 0.089 |
| 0.5 × 0.049 | 12.70 × 1.24 | 0.081 | 0.121 |
| 0.5 × 0.065 | 12.70 × 1.65 | 0.104 | 0.155 |
| 0.75 × 0.049 | 19.05 × 1.24 | 0.126 | 0.188 |
| 0.75 × 0.065 | 19.05 × 1.65 | 0.164 | 0.244 |
| 0.75 × 0.083 | 19.05 × 2.11 | 0.203 | 0.303 |
| 1 × 0.049 | 25.40 × 1.24 | 0.171 | 0.255 |
| 1 × 0.065 | 25.40 × 1.65 | 0.223 | 0.332 |
| 1 × 0.125 | 25.40 × 3.17 | 0.402 | 0.598 |
| 1.25 × 0.065 | 31.75 × 1.65 | 0.283 | 0.421 |
| 1.25 × 0.125 | 31.75 × 3.17 | 0.517 | 0.769 |
| 1.5 × 0.065 | 38.10 × 1.65 | 0.343 | 0.510 |
| 1.5 × 0.125 | 38.10 × 3.17 | 0.632 | 0.940 |
| 1.5 × 0.250 | 38.10 × 6.35 | 1.149 | 1.709 |
| 2 × 0.065 | 50.80 × 1.65 | 0.462 | 0.688 |
| 2 × 0.125 | 50.80 × 3.17 | 0.861 | 1.282 |
| 2 × 0.250 | 50.80 × 6.35 | 1.608 | 2.393 |
| 2.5 × 0.125 | 63.50 × 3.17 | 1.091 | 1.624 |
| 2.5 × 0.250 | 63.50 × 6.35 | 2.068 | 3.077 |
| 3 × 0.125 | 76.20 × 3.17 | 1.321 | 1.966 |
| 3 × 0.250 | 76.20 × 6.35 | 2.527 | 3.761 |
| 4 × 0.125 | 101.60 × 3.17 | 1.780 | 2.650 |
| 4 × 0.250 | 101.60 × 6.35 | 3.446 | 5.128 |
| 6 × 0.250 | 152.40 × 6.35 | 5.284 | 7.863 |
| 6 × 0.500 | 152.40 × 12.70 | 10.108 | 15.043 |
Tube weight rises almost in proportion to wall thickness, while bending stiffness rises with roughly the cube of the diameter. Increasing diameter at the same wall is therefore usually the most weight-efficient way to make a tube stiffer, as long as the wall does not become so thin that it dents or buckles locally. Use the tube weight calculator for other sizes.
| Standard | Scope |
|---|---|
| ASTM B221 | Extruded bars, rods, wire, profiles and tubes, including porthole tube |
| ASTM B241 / B241M | Seamless pipe and seamless extruded tube |
| ASTM B429 / B429M | Extruded structural pipe and tube |
| ASTM B210 / B210M | Drawn seamless tube |
| ASTM B483 / B483M | Drawn tube for general purpose applications |
| ASTM B313 / B313M | Welded round tube |
| ASTM B491 / B491M | Extruded round tube for general purpose applications |
| AMS-QQ-A-200 / AMS-WW-T-700 | Aerospace extruded and drawn tube by alloy, replacing federal QQ-A-200 and WW-T-700 |
| EN 755-2, -7, -8 | Extruded tube: mechanical properties, seamless tube tolerances, porthole tube tolerances |
| EN 754-2, -7, -8 | Cold-drawn tube: mechanical properties and tolerances for seamless and porthole drawn tube |
Tolerances on OD, wall, ovality, straightness and length are set by the standard named on the order. EN 755-7 and EN 755-8 have different tables for seamless and porthole tube, and ASTM orders take tolerances from ANSI H35.2. If concentricity or wall uniformity is critical, for example for telescopic poles or tube that will be bored, say so: seamless drawn tube holds wall thickness more evenly than as-extruded tube.
Soft tempers (O, T4) and 3003, 5052 or 6063 bend most easily. As a starting point, mandrel bending of 6061-T6 needs a centre-line radius of several times the OD; thin walls need a mandrel and wiper die to prevent wrinkling. For tight bends, bend in T4 or O and heat-treat afterwards.
6061, 6063, 6082 and the 5xxx alloys weld by TIG or MIG with 4043 or 5356 filler. Heat-treated 6xxx tube loses strength in the heat-affected zone, so welded frames are designed to reduced allowable stresses.
Swaging, flaring, crimping and compression fittings suit 3003, 5052 and 6061 in softer tempers. Avoid galvanic contact with copper and plain steel fittings in wet service.
Tube is turned, bored and threaded like bar; support thin walls to prevent chatter and distortion, and use sharp tools with high positive rake.
6063 and 6060 give the most uniform decorative anodising; 6061 anodises well; 2024 and 7075 take hard anodising but look darker.
5xxx and 6xxx tube resists the weather and seawater well; 2024 and 7075 should be anodised or painted in damp or marine service.
Seamless tube is extruded over a mandrel and has no joint in the wall. Structural (porthole) tube is extruded through a bridge die, so the metal splits and re-welds inside the die, leaving longitudinal seam welds. Both are strong enough for structures, but pressure applications normally require seamless tube.
6061-T6 for anything load-bearing: its typical yield strength is about 276 MPa against 214 MPa for 6063-T6 and 145 MPa for 6063-T5. 6063 is better where appearance and anodising matter more than strength, such as handrails and furniture.
Weight in kg/m = 0.0084823 × wall × (OD − wall), with dimensions in millimetres. A 50 × 3 mm tube weighs about 1.20 kg/m. In inches, lb/ft = 3.676 × wall × (OD − wall).
Not for structural joints: 7075 is prone to hot cracking and loses strength when fusion-welded. Use 6061 or the weldable 7xxx alloys 7005 and 7020 for welded frames.
Tube is ordered by actual outside diameter and wall thickness. Pipe is ordered by nominal pipe size and schedule (for example NPS 2 Schedule 40), where the OD is fixed for each size and wall varies with schedule.
In the US, ASTM B221 for extruded tube, B241 for seamless tube, B210 and B483 for drawn tube and B313 for welded tube. In Europe, EN 755 for extruded and EN 754 for cold-drawn tube.
Tell us the alloy, temper, OD, wall, length and whether seamless is required. We will confirm the right tube type, certification and a delivered price.
