SUS304 Stainless Steel Pipe Wall Thickness Chart: Schedules 5S to 80S

Why wall thickness decides SUS304 pipe performance

Wall thickness is the single variable that links the four things a buyer cares about in a SUS304 (UNS S30400, EN 1.4301) pipe: internal pressure rating, corrosion allowance, structural stiffness and total cost. Under ASME B31.3 the allowable stress for 304 at ambient temperature is 137.9 MPa (20.0 ksi), so the pressure a line can hold rises almost linearly with wall thickness once the outside diameter is fixed.

Pressure resistance – thicker walls raise the burst and allowable working pressure of the line.

Corrosion allowance – a heavier wall keeps chloride and acid service inside the design life.

Stiffness – wall thickness, not grade, controls deflection in long unsupported runs.

Cost – pipe weight per metre scales with thickness, so every extra schedule step is paid for in freight and material.

SUS304 pipe wall thickness chart (ASME B36.19M schedules)

The table below lists nominal wall thickness in millimetres for stainless steel pipe to ASME B36.19M, the schedule system that defines the 5S, 10S, 40S and 80S series. Millimetre values are shown first with the inch equivalent, because SUS304 pipe to JIS G3459 is normally ordered on outside diameter and wall in millimetres.

NPS	OD (mm)	Sch 5S	Sch 10S	Sch 40S	Sch 80S
1/8	10.3	1.24 mm (0.049")	1.73 mm (0.068")	2.41 mm (0.095")	3.28 mm (0.129")
1/4	13.7	1.65 mm (0.065")	2.24 mm (0.088")	3.02 mm (0.119")	3.68 mm (0.145")
3/8	17.1	1.65 mm (0.065")	2.31 mm (0.091")	3.20 mm (0.126")	4.05 mm (0.159")
1/2	21.3	1.65 mm (0.065")	2.11 mm (0.083")	2.77 mm (0.109")	3.73 mm (0.147")
3/4	26.7	1.65 mm (0.065")	2.11 mm (0.083")	2.87 mm (0.113")	3.91 mm (0.154")
1	33.4	1.65 mm (0.065")	2.77 mm (0.109")	3.38 mm (0.133")	4.55 mm (0.179")
1 1/4	42.2	1.65 mm (0.065")	2.77 mm (0.109")	3.56 mm (0.140")	4.85 mm (0.191")
1 1/2	48.3	1.65 mm (0.065")	2.77 mm (0.109")	3.68 mm (0.145")	5.08 mm (0.200")
2	60.3	1.65 mm (0.065")	2.77 mm (0.109")	3.91 mm (0.154")	5.54 mm (0.218")
2 1/2	73.0	2.11 mm (0.083")	3.05 mm (0.120")	5.16 mm (0.203")	7.01 mm (0.276")
3	88.9	2.11 mm (0.083")	3.05 mm (0.120")	5.49 mm (0.216")	7.62 mm (0.300")
4	114.3	2.11 mm (0.083")	3.05 mm (0.120")	6.02 mm (0.237")	8.56 mm (0.337")
5	141.3	2.77 mm (0.109")	3.40 mm (0.134")	6.55 mm (0.258")	9.53 mm (0.375")
6	168.3	2.77 mm (0.109")	3.40 mm (0.134")	7.11 mm (0.280")	10.97 mm (0.432")
8	219.1	2.77 mm (0.109")	3.76 mm (0.148")	8.18 mm (0.322")	12.70 mm (0.500")
10	273.1	3.40 mm (0.134")	4.19 mm (0.165")	9.27 mm (0.365")	15.09 mm (0.594")
12	323.9	3.96 mm (0.156")	4.57 mm (0.180")	10.31 mm (0.406")	17.48 mm (0.688")

Two points deserve attention. First, the S-series stops at 80S; there is no Schedule 160S in ASME B36.19M, and heavy-wall SUS304 pipe is instead ordered on the ASME B36.10M schedules or on a millimetre wall. Second, wall thickness tolerance follows the product standard: ASTM A312 seamless pipe carries a ±12.5% wall tolerance, while welded pipe carries no minimum wall unless it is ordered as A312 with a minimum-wall note. Always confirm which table and which tolerance the mill certificate references.

Typical applications by schedule

Schedule	Typical wall (NPS 2)	Service
5S	1.65 mm	Ventilation ducts, HVAC, low-pressure instrument air
10S	2.77 mm	Chemical processing, water treatment, low-pressure transfer lines
40S	3.91 mm	General industrial piping, food and beverage, pharmaceutical skids
80S	5.54 mm	Fire protection, hydraulic lines, marine and offshore service

How to calculate SUS304 pipe weight per metre

Weight drives freight cost, support spacing and lifting plans, so it is worth calculating rather than estimating. For a round pipe:

W (kg/m) = π × t × (OD − t) × ρ / 1000

t = nominal wall thickness (mm)

OD = outside diameter (mm)

ρ = density of 304 stainless steel, 7.93 g/cm³ (7,930 kg/m³)

π = 3.1416

Working that through gives the practical mill formula W (kg/m) = 0.02491 × t × (OD − t). A 4 inch Schedule 40S pipe with OD 114.3 mm and wall 6.02 mm therefore weighs 0.02491 × 6.02 × 108.28 = 16.2 kg/m. The same formula is used for 304L and 316L pipe because the density difference between the grades is under 0.5%.

Selecting thickness for pressure and corrosion

Start from the design pressure and the allowable stress of 137.9 MPa at ambient temperature, then add a corrosion allowance and check the result against the nearest available schedule rather than designing a non-standard wall. In chloride service above about 60 °C, 304 is prone to pitting and stress corrosion cracking, so the fix is a change of grade (316L or duplex) rather than a thicker 304 wall. Where the line runs warm and stagnant, flush and drain points do more for life than an extra millimetre of steel.

FAQ

Q: Does SUS304 pipe follow the same schedule table as carbon steel?
Partly. The 5S, 10S, 40S and 80S series come from ASME B36.19M and apply to stainless steel only. The heavier 10, 20, 30, 40, 60, 80, 100, 120, 140 and 160 schedules come from ASME B36.10M and are widely quoted for stainless pipe as well.

Q: Is there a Schedule 160S for SUS304 pipe?
No. ASME B36.19M defines only the S-series up to 80S. If a heavy wall is needed, specify an ASME B36.10M schedule such as Sch 160 or state the wall in millimetres on the purchase order.

Q: What wall tolerance should be expected?
ASTM A312 specifies ±12.5% on wall for seamless pipe. Welded pipe is normally supplied at the nominal wall with a minimum-wall option available, and JIS G3459 sets its own tolerance band, so the mill certificate must be checked against the ordering standard.

Q: How do I convert an inch wall thickness to millimetres?
Multiply by 25.4. A 0.109 inch wall is 2.77 mm, and a 0.237 inch wall is 6.02 mm. Nominal values are rounded, so always use the published millimetre figure when the pipe is ordered to a metric standard.

Q: Which schedule is used for potable water?
Schedule 10S is common for cold potable water and Schedule 40S for pumped or buried lines, in both cases with welded joints that are passivated to ASTM A380 after fabrication so the chromium oxide layer is fully restored.

Q: Can I use a thinner wall to reduce cost?
Only if the line pressure, corrosion allowance and support spacing all still pass. Reducing wall below the next schedule down usually fails the pressure check long before it saves material cost, and it weakens the pipe against mechanical damage during installation.