Square tubing sizes are stated as outside width × outside width × wall thickness, for example 50 × 50 × 2.0 mm or 2 × 2 × 0.083 in. Stainless square tube runs from small sections around 10 × 10 mm up to 16 in. (406.4 mm) under ASTM A554. The standard sets the tolerances, not a fixed list of sizes, so the charts below show common sizes with their weight and A554 limits.
Tolerances, corner radii, twist, squareness and straightness are from ASTM A554-26 (Tables 5, 6 and 7), the standard for welded stainless steel mechanical tubing. Weights are calculated with the formula on this page and are not part of the standard.
Metric square tube size chart
Common stainless sections with calculated weight. The tolerance and corner radius columns apply the A554-26 limits to each size. Other sizes and walls are possible; TeCarve quotes square tube from 3 × 3 to 300 × 300 mm with walls of 0.5 to 6.0 mm.
| Size, mm (width × width × wall) | Width, in. | Wall, in. | Weight, kg/m | Weight, lb/ft | Across flats, ±mm | Corner radius max, mm |
|---|---|---|---|---|---|---|
| 10 × 10 × 1.0 | 0.394 | 0.039 | 0.29 | 0.19 | ±0.38 | 2.4 |
| 12 × 12 × 1.0 | 0.472 | 0.039 | 0.35 | 0.23 | ±0.38 | 2.4 |
| 15 × 15 × 1.2 | 0.591 | 0.047 | 0.53 | 0.35 | ±0.38 | 2.4 |
| 20 × 20 × 1.2 | 0.787 | 0.047 | 0.72 | 0.48 | ±0.38 | 2.4 |
| 20 × 20 × 1.5 | 0.787 | 0.059 | 0.88 | 0.59 | ±0.38 | 3.2 |
| 25 × 25 × 1.5 | 0.984 | 0.059 | 1.12 | 0.75 | ±0.38 | 3.2 |
| 25 × 25 × 1.6 | 0.984 | 0.063 | 1.19 | 0.80 | ±0.38 | 3.2 |
| 30 × 30 × 1.5 | 1.181 | 0.059 | 1.36 | 0.91 | ±0.38 | 3.2 |
| 40 × 40 × 1.5 | 1.575 | 0.059 | 1.83 | 1.23 | ±0.51 | 3.2 |
| 40 × 40 × 1.6 | 1.575 | 0.063 | 1.95 | 1.31 | ±0.51 | 3.2 |
| 40 × 40 × 2.0 | 1.575 | 0.079 | 2.41 | 1.62 | ±0.51 | 4.0 |
| 50 × 50 × 2.0 | 1.969 | 0.079 | 3.05 | 2.05 | ±0.51 | 4.0 |
| 50 × 50 × 2.3 | 1.969 | 0.091 | 3.48 | 2.34 | ±0.51 | 4.8 |
| 60 × 60 × 2.0 | 2.362 | 0.079 | 3.68 | 2.47 | ±0.51 | 4.0 |
| 60 × 60 × 2.5 | 2.362 | 0.098 | 4.56 | 3.06 | ±0.51 | 5.6 |
| 75 × 75 × 2.3 | 2.953 | 0.091 | 5.30 | 3.56 | ±0.76 | 4.8 |
| 75 × 75 × 2.5 | 2.953 | 0.098 | 5.75 | 3.86 | ±0.76 | 5.6 |
| 80 × 80 × 3.0 | 3.150 | 0.118 | 7.33 | 4.92 | ±0.76 | 6.8 |
| 100 × 100 × 3.0 | 3.937 | 0.118 | 9.23 | 6.20 | ±0.76 | 6.8 |
| 100 × 100 × 3.2 | 3.937 | 0.126 | 9.83 | 6.60 | ±0.76 | 6.8 |
| 120 × 120 × 4.0 | 4.724 | 0.157 | 14.72 | 9.89 | ±0.76 | 11.1 |
| 150 × 150 × 4.0 | 5.906 | 0.157 | 18.52 | 12.45 | ±1.52 | 11.1 |
Square tubing sizes in inches
A554 states its values in inch-pound units and treats the mm figures as conversions. These examples show how the same limits apply to inch sizes. Give the wall as a decimal rather than a gauge number, because gauge tables differ, and confirm availability of inch sizes when you request a quote.
| Size, in. (width × width × wall) | Weight, lb/ft | Weight, kg/m | Across flats, ±in. | Corner radius max, in. |
|---|---|---|---|---|
| 1 × 1 × 0.065 | 0.84 | 1.24 | ±0.015 | 1/8 |
| 1 1/4 × 1 1/4 × 0.065 | 1.06 | 1.58 | ±0.015 | 1/8 |
| 1 1/2 × 1 1/2 × 0.065 | 1.28 | 1.91 | ±0.020 | 1/8 |
| 1 1/2 × 1 1/2 × 0.083 | 1.62 | 2.41 | ±0.020 | 5/32 |
| 2 × 2 × 0.065 | 1.73 | 2.57 | ±0.020 | 1/8 |
| 2 × 2 × 0.083 | 2.19 | 3.26 | ±0.020 | 5/32 |
| 2 × 2 × 0.120 | 3.10 | 4.62 | ±0.020 | 17/64 |
| 2 1/2 × 2 1/2 × 0.083 | 2.76 | 4.11 | ±0.020 | 5/32 |
| 2 1/2 × 2 1/2 × 0.120 | 3.93 | 5.84 | ±0.020 | 17/64 |
| 3 × 3 × 0.120 | 4.75 | 7.07 | ±0.030 | 17/64 |
| 4 × 4 × 0.120 | 6.40 | 9.53 | ±0.030 | 17/64 |
| 4 × 4 × 0.188 | 9.86 | 14.67 | ±0.030 | 7/16 |
| 6 × 6 × 0.188 | 15.03 | 22.36 | ±0.060 | 7/16 |
How to calculate square tube weight
Weight per length = 4 × (width − wall) × wall × density. The charts use a density of 7.93 g/cm³ and ignore the rounded corners, so real tube is slightly lighter than the calculated figure. Use a density that suits your grade when the weight matters, and use the actual weight on the mill test certificate or packing list for shipping.
- Metric: kg/m = 4 × (W − t) × t × 0.00793, with W and t in mm. For 50 × 50 × 2.0 mm: 4 × 48 × 2.0 × 0.00793 = 3.05 kg/m.
- Inch: lb/ft = 4 × (W − t) × t × 12 × 0.2865, with W and t in inches. For 2 × 2 × 0.083 in.: 2.19 lb/ft.
- Rectangular tube: replace 4 × (W − t) with 2 × (W + H − 2t). The tolerance is set by the largest side. See our rectangular tube sizes chart and stainless steel rectangular tube.
ASTM A554 tolerances for square and rectangular tubing
Outside dimension (Table 5)
| Largest outside dimension across flats, in. (mm) | Tolerance across flats, including convexity or concavity, ±in. (mm) |
|---|---|
| To 1 1/4 (31.8), incl | 0.015 (0.38) |
| Over 1 1/4 to 2 1/2 (31.8 to 63.5), incl | 0.020 (0.51) |
| Over 2 1/2 to 5 1/2 (63.5 to 139.7), incl | 0.030 (0.76) |
| Over 5 1/2 to 8 (139.7 to 203.2), incl | 0.060 (1.52) |
| Over 8 to 12 (203.2 to 304.8), incl | 0.080 (2.03) |
| Over 12 to 16 (304.8 to 406.4), incl | 0.125 (3.18) |
Wall thickness tolerance is ±10 % of the nominal wall. For sizes over 16 in. (406 mm), A554 says to consult the tube manufacturer.
Corner radius (Table 6)
| Wall thickness, in. (mm) | Corner radius, max, in. (mm) |
|---|---|
| Over 0.020 to 0.049 (0.51 to 1.24), incl | 3/32 (2.4) |
| Over 0.049 to 0.065 (1.24 to 1.65), incl | 1/8 (3.2) |
| Over 0.065 to 0.083 (1.65 to 2.11), incl | 5/32 (4.0) |
| Over 0.083 to 0.095 (2.11 to 2.42), incl | 3/16 (4.8) |
| Over 0.095 to 0.109 (2.42 to 2.77), incl | 7/32 (5.6) |
| Over 0.109 to 0.134 (2.77 to 3.40), incl | 17/64 (6.8) |
| Over 0.134 to 0.156 (3.40 to 3.96), incl | 5/16 (8.0) |
| Over 0.156 to 0.200 (3.96 to 5.08), incl | 7/16 (11.1) |
| Over 0.200 to 0.250 (5.08 to 6.35), incl | 9/16 (14.3) |
| Over 0.250 to 0.350 (6.35 to 8.90), incl | 7/8 (22.2) |
| Over 0.350 to 0.500 (8.90 to 12.70), incl | 1 1/2 (38.1) |
| Over 0.500 to 0.625 (12.70 to 15.88), incl | 1 7/8 (47.6) |
For sizes over 0.625 in. (15.88 mm), A554 says to consult the tube manufacturer about corner radii. The radius is measured as the Effective Corner Radius: ECR = (tube width − width of flat) / 2. The example in A554 Figure 1 is a 4 in. wide shape with a 3 in. flat, which gives an ECR of 0.5 in. Tighter corners have to be agreed on the order.
Twist, squareness and straightness (Table 7)
| Largest size, in. (mm) | Twist in 3 ft (1 m), max, in. (mm) | Twist in 20 ft (6 m), max, in. (mm) |
|---|---|---|
| Under 1 1/2 (38.1), incl | 0.050 (1.27) | 0.333 (8.45) |
| Over 1 1/2 to 2 1/2 (38.1 to 63.5), incl | 0.062 (1.57) | 0.413 (10.5) |
| Over 2 1/2 to 4 (63.5 to 101.6), incl | 0.075 (1.90) | 0.500 (12.7) |
| Over 4 to 6 (101.6 to 152.4), incl | 0.087 (2.21) | 0.580 (14.7) |
| Over 6 to 8 (152.4 to 203.2), incl | 0.100 (2.54) | 0.667 (16.9) |
| Over 8 (203.2) | 0.112 (2.84) | 0.747 (19.0) |
- Squareness of sides: ±B = C × 0.006, where B is the out-of-square tolerance and C is the length of the longest side. For a 100 mm side that is ±0.6 mm.
- Straightness: 0.075 in. in 3 ft, or 2.1 mm in 1 m, checked with a 3-ft (1-m) straightedge and feeler gauge.
What to specify when ordering square tube
- Size: outside width × outside width × wall, and whether the wall is given in mm or inches. Use the mm to inches converter if your drawing uses a different unit.
- Standard and grade: for example ASTM A554, 304 or 316L. See the ASTM A554 guide for the full requirements.
- Condition: A554 supplies square and rectangular welded tube as cold worked unless otherwise specified, so state it if you need annealed tube.
- Length: A554 mill lengths are 5 ft (1.5 m) and over. Definite cut lengths are furnished when specified.
- Surface finish: state the grit or finish; A554 requires it in the order if special surface conditioning is needed. The surface finish chart explains Ra values.
- Corner radius: state it if you need tighter corners than Table 6 allows, for example for fit-up or welded frames.
TeCarve supplies stainless steel square tube from the Foshan Plant, which makes welded and decorative tube. Trial orders start from 100 to 300 kg; stocked sizes ship in 7 to 10 days and custom runs in 10 to 25 days. Each order comes with an EN 10204 3.1 mill test certificate issued by the producing plant. More charts are in our technical resources. For round tube, see the stainless steel tube size chart.
Frequently asked questions
What sizes does square tubing come in?
The common sections charted on this page run from 10 × 10 mm to 150 × 150 mm with walls of 1.0 to 4.0 mm. ASTM A554 covers sizes up to 16 in. (406.4 mm) with walls of 0.020 in. (0.51 mm) and over, but it does not fix a list of standard sizes.
How do you read a square tubing size?
The numbers are outside width × outside width × wall thickness. 50 × 50 × 2.0 means a section 50 mm wide on each side with a 2.0 mm wall.
What is the tolerance on 2 x 2 square tubing?
Under ASTM A554-26 Table 5, a 2 in. section is in the over 1 1/4 to 2 1/2 in. band, so the tolerance across flats is ±0.020 in. (0.51 mm). The wall tolerance is ±10 %.
How much does stainless steel square tube weigh?
Use kg/m = 4 × (W − t) × t × 0.00793, with W and t in mm. A 50 × 50 × 2.0 mm tube works out at about 3.05 kg/m (2.05 lb/ft) before allowing for the rounded corners.
What is the corner radius of square tubing?
ASTM A554 sets a maximum that rises with the wall. It is 3/32 in. (2.4 mm) for walls up to 0.049 in. (1.24 mm) and 17/64 in. (6.8 mm) for walls over 0.109 to 0.134 in. (2.77 to 3.40 mm).
Is ASTM A554 square tube suitable for pressure service?
A554 is a mechanical tubing specification for ornamental, structural, exhaust and other applications where appearance, mechanical properties or corrosion resistance is needed. Check your design code before using it under pressure.
