Pipe Schedule Chart — Pipe Dimensions, Wall Thickness & Weight
A complete, engineer-grade reference for nominal pipe size (NPS), outside diameter (OD), wall thickness, inside diameter (ID) and theoretical weight across schedules SCH 5 through XXS. Filter by material and standard, switch between millimetres and inches, compare schedules for any size, and estimate weight for your BOQ before you raise an RFQ.
Pipe Schedule Chart — OD, Wall, ID & Weight
Choose a dimensional standard, schedule and material, then switch units. Outside diameter and wall thickness are the standardised values; inside diameter and weight are computed from them (ID = OD − 2 × wall; weight uses the selected material density).
Outside diameter is constant for a given NPS regardless of schedule — only the wall thickness (and therefore the bore) changes. Weights are nominal/theoretical values for estimating; confirm mill tolerances and actual mass on the material test certificate.
Compare every schedule for one size
Pick a nominal size to see how wall thickness, bore and weight change across all available schedules — carbon/alloy (B36.10M) and stainless (B36.19M) together. Outside diameter stays fixed; the pipe simply gets heavier and its bore smaller as the schedule increases.
Outside diameter · — constant across every schedule below.
Estimate weight for your BOQ
Enter size, schedule, material, length and quantity to get outside diameter, wall thickness, bore, metal cross-section area and theoretical weight per metre, per piece and total — then send those exact figures straight to our team as an enquiry.
Calculated Result
Metal cross-section area = π × t × (OD − t). Weight is theoretical and based on nominal dimensions and typical density; actual dispatch weight is confirmed on the material test certificate.
Outside diameter, wall thickness & bore
Fixed by the NPS and standard. It never changes with schedule, so fittings and flanges of the same NPS always mate.
Set by the schedule number. A higher schedule means a thicker wall for the same OD.
What is left for flow. It is derived, not tabulated separately:
ID = OD − 2 × tWhat is a pipe schedule?
"Schedule" (SCH) is a designation for the wall thickness of a pipe of a given nominal size. It originated as an approximate index of pressure-carrying capacity — loosely related to the ratio of internal pressure to allowable stress — which is why higher schedule numbers correspond to thicker walls.
It is a designation, not a measurement
The schedule number is not a dimension in millimetres or inches. "SCH 40" does not mean 40 mm or 40 anything — it is an index that maps, through the standard, to a specific wall thickness for each nominal size.
Same schedule, different wall
Because it is an index, the actual wall thickness for a given schedule differs from size to size. SCH 40 on a 2" pipe is 3.91 mm; SCH 40 on a 12" pipe is 10.31 mm.
OD stays constant
For a given NPS, the outside diameter is fixed. Increasing the schedule adds metal inward, thickening the wall and reducing the bore — the OD is unchanged so joints stay compatible.
NPS vs DN vs actual OD
NPS (Nominal Pipe Size, inch-based) and DN (Diamètre Nominal, metric) are two naming systems for the same pipes. Neither is the real outside diameter for small sizes — the true OD is a separate standardised value. For example, NPS 2 = DN 50, but the actual OD is 60.3 mm, not 50 mm.
| NPS | DN | Actual OD (mm) | Actual OD (in) | Note |
|---|---|---|---|---|
| 1/2" | DN 15 | 21.3 | 0.840 | OD ≠ nominal |
| 1" | DN 25 | 33.4 | 1.315 | OD ≠ nominal |
| 2" | DN 50 | 60.3 | 2.375 | OD ≠ nominal |
| 4" | DN 100 | 114.3 | 4.500 | OD ≠ nominal |
| 8" | DN 200 | 219.1 | 8.625 | OD ≠ nominal |
| 14" | DN 350 | 355.6 | 14.000 | OD = nominal (14"+) |
| 24" | DN 600 | 609.6 | 24.000 | OD = nominal (14"+) |
From NPS 14" (DN 350) upward, the nominal size and the actual outside diameter coincide (14" = 355.6 mm = 14.000 in). Below that, always work from the tabulated OD, not the nominal label.
SCH 40 vs SCH 80
SCH 40 and SCH 80 are the two most commonly stocked schedules. For the same NPS they share an identical outside diameter; SCH 80 simply has a thicker wall, so it is heavier and has a smaller bore. Whether that thicker wall is actually needed depends on the design pressure, temperature, corrosion allowance, material and applicable code — not on the schedule number alone.
- Wall: thinner — e.g. 4" = 6.02 mm
- Bore: larger — more flow area for the same OD
- Weight: lighter — 4" carbon ≈ 16.1 kg/m
- Typical use: general utilities, low/moderate pressure, water, air and process lines within allowable limits
- Wall: thicker — e.g. 4" = 8.56 mm
- Bore: smaller — reduced flow area, higher velocity
- Weight: heavier — 4" carbon ≈ 22.3 kg/m
- Typical use: higher design pressure, mechanical loading, threading, or where a corrosion allowance is required
A thicker wall generally raises the pressure a pipe can withstand and adds corrosion allowance, but pressure rating is a calculation (per ASME B31.3 or the relevant code) involving material allowable stress, temperature, joint efficiency and corrosion allowance. Do not assume "SCH 80 is stronger" as a blanket rule — confirm against the design case.
STD, XS and XXS explained
Before numbered schedules, walls were called Standard (STD), Extra Strong (XS) and Double Extra Strong (XXS). These older designations still appear on drawings and in stock lists. STD and XS coincide with SCH 40 and SCH 80 only over part of the size range; XXS has no fixed schedule equivalent.
| Designation | Coincides with | Valid over | Above that range |
|---|---|---|---|
| STD (Standard) | SCH 40 | up to NPS 10" | STD holds at 9.53 mm (0.375") wall; SCH 40 keeps increasing |
| XS (Extra Strong) | SCH 80 | up to NPS 8" | XS holds at 12.70 mm (0.500") wall; SCH 80 keeps increasing |
| XXS (Double Extra Strong) | no fixed schedule | defined per size | heaviest legacy wall; roughly ~2 × XS on smaller sizes, size-specific |
Example of the divergence: at NPS 12", STD = 9.53 mm but SCH 40 = 10.31 mm, and XS = 12.70 mm but SCH 80 = 17.48 mm. Always confirm the exact wall from the size-specific table rather than assuming STD = 40 / XS = 80 everywhere.
ASME B36.10M vs B36.19M
Two ASME standards define pipe dimensions. They set the geometry only — the outside diameters and wall thicknesses — and are kept separate from the material specification (the ASTM/ASME grade), which defines chemistry, mechanical properties and manufacture.
- Scope: welded and seamless wrought steel pipe — carbon and alloy steel
- Schedules: 5, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160 plus STD, XS, XXS
- Used with grades like: ASTM A106, A53, A333, API 5L, A335 alloy
- Scope: stainless steel pipe geometry
- Schedules: the "S" schedules — 5S, 10S, 40S, 80S (thinner-walled set)
- Used with grades like: ASTM A312 / A358 (304/L, 316/L, 321, duplex)
The "S" in 5S / 10S / 40S / 80S denotes the stainless (B36.19M) wall series. For many sizes 40S equals SCH 40 and 80S equals SCH 80, but the S set also defines thin walls (5S, 10S) suited to corrosion-resistant stainless where full carbon-steel wall thickness is not required. A stainless pipe can still be ordered to a B36.10M wall — the standard describes geometry, the grade describes the metal.
Material selection alongside schedule
Schedule fixes the geometry; the material specification fixes what the pipe is made of. A complete pipe callout carries both — for example "NPS 6, SCH 40, ASTM A106 Gr. B". Choose the family by service conditions, then confirm the exact grade and standard.
Stainless Steel
A312 / A358 · 304, 304L, 316, 316L, 321, 347, 904LCorrosion resistance for process, food, pharma and chemical service. 316/L adds molybdenum for chloride and acid resistance.
Carbon Steel
A106 · A53 · API 5L · A333 (low-temp)The workhorse for pressure, utility and structural lines. A106/A53 for general service; API 5L for line pipe; A333 for low-temperature.
Alloy Steel
A335 · P5, P9, P11, P22, P91Chromium-molybdenum grades for high-temperature and high-pressure service such as power, refinery and boiler piping.
Duplex / Super Duplex
S31803, S32205, S32750, S32760High strength plus excellent chloride and pitting resistance for offshore, marine, desalination and aggressive process duty.
High Nickel Alloys
Inconel · Incoloy · Monel · Hastelloy · Nickel 200/201Severe corrosion, high-temperature and specialised chemical environments where stainless is not sufficient.
Keep the dimensional standard (B36.10M / B36.19M) separate from the material specification (ASTM/ASME grade) on every enquiry — the first sets size and wall, the second sets metallurgy and testing.
Pipe weight formula
The weight-per-metre figures in the tables and calculator are theoretical, computed from the standardised dimensions and the material density. The metal is a thin cylindrical shell, so:
where t = wall thickness (mm), OD = outside diameter (mm), ρ = density (kg/m³). The 10⁻⁶ converts mm² of cross-section into m². Inside diameter is ID = OD − 2t.
Typical densities
Carbon & alloy steel ≈ 7850 kg/m³, stainless ≈ 8000 kg/m³, duplex ≈ 7800 kg/m³, nickel alloys ≈ 8190–8890 kg/m³. The calculator uses a representative value per family.
Why "theoretical"
The formula uses nominal dimensions. Real pipe varies within mill tolerance, so actual weight differs slightly. For dispatch and invoicing, the material test certificate governs.
Worked example
4" SCH 40 carbon steel: OD 114.3 mm, wall 6.02 mm → π × 6.02 × (114.3 − 6.02) × 7850 × 10⁻⁶ ≈ 16.1 kg/m.
Pipe schedule — frequently asked
Does a higher schedule always mean higher pressure capacity?
A higher schedule gives a thicker wall, which generally increases the pressure a pipe can withstand and can provide corrosion allowance. But the actual pressure rating is a calculation under ASME B31.3 (or the applicable code) that depends on the material's allowable stress at temperature, weld joint efficiency and corrosion allowance — not on the schedule number by itself. Always verify against the design conditions.
Is the schedule number a measurement in millimetres?
No. The schedule is a designation, not a dimension. "SCH 40" does not equal 40 mm. It is an index that maps to a specific wall thickness for each nominal size through the ASME standard, so the same schedule gives different wall thicknesses on different sizes.
What is the difference between NPS and DN?
They are two naming systems for the same pipe — NPS is inch-based, DN is metric. NPS 2 = DN 50. Neither equals the real outside diameter on small sizes: NPS 2 / DN 50 actually has a 60.3 mm OD. From NPS 14" upward, the nominal size and the actual OD coincide.
Are STD, XS and XXS the same as SCH 40, 80 and 160?
Only partly. STD equals SCH 40 up to NPS 10", and XS equals SCH 80 up to NPS 8"; beyond those sizes STD stays at 9.53 mm and XS at 12.70 mm while the numbered schedules keep increasing. XXS has no single schedule equivalent and is defined per size.
What is the difference between B36.10M and B36.19M?
B36.10M defines dimensions for carbon and alloy steel pipe (schedules 5–160, STD/XS/XXS). B36.19M defines the stainless "S" schedules (5S, 10S, 40S, 80S). Both are dimensional standards only and are used together with a material specification such as ASTM A106 or A312.
Are the weights on this page exact?
They are theoretical, computed from nominal dimensions and typical densities using Weight = π × t × (OD − t) × ρ × 10⁻⁶. Actual pipe weight varies within mill tolerance; the material test certificate is the governing figure for dispatch and invoicing.
Have your sizes ready? Let us quote them.
Share NPS/OD, schedule or wall, grade, standard, length and quantity — our team confirms grade, schedule and standard-wise availability and returns a costed RFQ with documentation options.
