Smart Pipe Size Calculator
Pick a nominal pipe size (NPS or DN) and a schedule — get outer diameter, wall thickness, inner diameter, cross-section area, steel weight per metre, and fluid volume per metre instantly, with a true-scale cross-section preview. Searchable full ASME B36.10M chart, metric / imperial toggle, every value live-calculated.
Carbon-steel weight estimate (ρ = 7850 kg/m³). For copper × 1.14, stainless × 1.02, PVC × 0.18. Dimensions per ASME B36.10M.
Full reference table
| NPS | DN | OD (mm) | OD (in) | SCH 10 | SCH 20 | SCH 40 | SCH 80 | SCH 160 | SCH XXS |
|---|---|---|---|---|---|---|---|---|---|
| 1/8" | DN 6 | 10.29 | 0.405 | — | — | 1.73ID 6.8 | 2.41ID 5.5 | — | — |
| 1/4" | DN 8 | 13.72 | 0.540 | — | — | 2.24ID 9.2 | 3.02ID 7.7 | — | — |
| 3/8" | DN 10 | 17.15 | 0.675 | — | — | 2.31ID 12.5 | 3.20ID 10.7 | — | — |
| 1/2" | DN 15 | 21.34 | 0.840 | 2.11ID 17.1 | — | 2.77ID 15.8 | 3.73ID 13.9 | 4.78ID 11.8 | 7.47ID 6.4 |
| 3/4" | DN 20 | 26.67 | 1.050 | 2.11ID 22.5 | — | 2.87ID 20.9 | 3.91ID 18.9 | 5.56ID 15.6 | 7.82ID 11.0 |
| 1" | DN 25 | 33.40 | 1.315 | 2.77ID 27.9 | — | 3.38ID 26.6 | 4.55ID 24.3 | 6.35ID 20.7 | 9.09ID 15.2 |
| 1-1/4" | DN 32 | 42.16 | 1.660 | 2.77ID 36.6 | — | 3.56ID 35.0 | 4.85ID 32.5 | 6.35ID 29.5 | 9.70ID 22.8 |
| 1-1/2" | DN 40 | 48.26 | 1.900 | 2.77ID 42.7 | — | 3.68ID 40.9 | 5.08ID 38.1 | 7.14ID 34.0 | 10.15ID 28.0 |
| 2" | DN 50 | 60.32 | 2.375 | 2.77ID 54.8 | — | 3.91ID 52.5 | 5.54ID 49.2 | 8.74ID 42.8 | 11.07ID 38.2 |
| 2-1/2" | DN 65 | 73.03 | 2.875 | 3.05ID 66.9 | — | 5.16ID 62.7 | 7.01ID 59.0 | 9.53ID 54.0 | 14.02ID 45.0 |
| 3" | DN 80 | 88.90 | 3.500 | 3.05ID 82.8 | — | 5.49ID 77.9 | 7.62ID 73.7 | 11.13ID 66.6 | 15.24ID 58.4 |
| 3-1/2" | DN 90 | 101.6 | 4.000 | 3.05ID 95.5 | — | 5.74ID 90.1 | 8.08ID 85.4 | — | — |
| 4" | DN 100 | 114.3 | 4.500 | 3.05ID 108.2 | — | 6.02ID 102.3 | 8.56ID 97.2 | 13.49ID 87.3 | 17.12ID 80.1 |
| 5" | DN 125 | 141.3 | 5.563 | 3.40ID 134.5 | — | 6.55ID 128.2 | 9.53ID 122.2 | 15.88ID 109.5 | 19.05ID 103.2 |
| 6" | DN 150 | 168.3 | 6.625 | 3.40ID 161.5 | — | 7.11ID 154.1 | 10.97ID 146.3 | 18.26ID 131.8 | 21.95ID 124.4 |
| 8" | DN 200 | 219.1 | 8.625 | 3.76ID 211.6 | 6.35ID 206.4 | 8.18ID 202.7 | 12.70ID 193.7 | 23.01ID 173.1 | 22.23ID 174.6 |
| 10" | DN 250 | 273.1 | 10.750 | 4.19ID 264.7 | 6.35ID 260.4 | 9.27ID 254.5 | 15.09ID 242.9 | 28.58ID 215.9 | 25.40ID 222.3 |
| 12" | DN 300 | 323.9 | 12.750 | 4.57ID 314.7 | 6.35ID 311.2 | 10.31ID 303.2 | 17.48ID 288.9 | 33.32ID 257.2 | 25.40ID 273.1 |
| 14" | DN 350 | 355.6 | 14.000 | 4.78ID 346.0 | 7.92ID 339.8 | 11.13ID 333.3 | 19.05ID 317.5 | 35.71ID 284.2 | — |
| 16" | DN 400 | 406.4 | 16.000 | 4.78ID 396.8 | 7.92ID 390.6 | 12.70ID 381.0 | 21.44ID 363.5 | 40.49ID 325.4 | — |
| 18" | DN 450 | 457.2 | 18.000 | 4.78ID 447.6 | 7.92ID 441.4 | 14.27ID 428.7 | 23.83ID 409.5 | 45.24ID 366.7 | — |
| 20" | DN 500 | 508.0 | 20.000 | 5.54ID 496.9 | 9.53ID 488.9 | 15.09ID 477.8 | 26.19ID 455.6 | 50.01ID 408.0 | — |
| 22" | DN 550 | 558.8 | 22.000 | 5.54ID 547.7 | 9.53ID 539.7 | — | 28.58ID 501.6 | 53.98ID 450.8 | — |
| 24" | DN 600 | 609.6 | 24.000 | 6.35ID 596.9 | 9.53ID 590.5 | 17.48ID 574.6 | 30.96ID 547.7 | 59.54ID 490.5 | — |
| 26" | DN 650 | 660.4 | 26.000 | 7.92ID 644.6 | — | — | — | — | — |
| 28" | DN 700 | 711.2 | 28.000 | 7.92ID 695.4 | — | — | — | — | — |
| 30" | DN 750 | 762.0 | 30.000 | 7.92ID 746.2 | — | — | — | — | — |
| 32" | DN 800 | 812.8 | 32.000 | 7.92ID 797.0 | — | — | — | — | — |
| 34" | DN 850 | 863.6 | 34.000 | 7.92ID 847.8 | — | — | — | — | — |
| 36" | DN 900 | 914.4 | 36.000 | 7.92ID 898.6 | — | — | — | — | — |
| 42" | DN 1050 | 1067 | 42.000 | — | — | — | — | — | — |
| 48" | DN 1200 | 1219 | 48.000 | — | — | — | — | — | — |
Wall thickness values shown in millimetres; ID computed as OD − 2 × wall. Click any row to load it above.
What makes this calculator different
Choose NPS and schedule — OD, wall, ID, area, weight per metre, and fluid volume per metre are all computed and shown at once. No flipping between tables.
The visual on the right is the actual pipe cross-section drawn to scale, with OD and ID called out. You see the wall, not just a number.
One toggle flips every value between mm/kg/L and in/lb/gal. Each spec also shows the alternate unit below in fine print so you never have to choose between the two.
The whole table is on this page — 32 nominal sizes from NPS 1/8" (DN 6) up to NPS 48" (DN 1200), with every standard schedule. Type any size to filter; click a row to load it above.
Inner diameter, weight, area and volume are calculated live from the underlying formulas — useful for non-standard combinations and for understanding the why, not just the what.
The calculator and table ship as static data. Nothing is uploaded; nothing is logged.
NPS, DN, and why a 2" pipe isn't actually 2 inches
Pipe is sized by a Nominal Pipe Size (NPS) in the US/Imperial system and a Diameter Nominal (DN) in the metric system. The two are different ways of labelling the same piece of pipe — they map one-to-one. For NPS ≤ 12", neither matches the pipe's real outer diameter:
- NPS 1/2" → OD 21.34 mm (≈ 0.84")
- NPS 1" → OD 33.40 mm (≈ 1.32")
- NPS 2" → OD 60.32 mm (≈ 2.37")
- NPS 14" → OD 355.60 mm = exactly 14.0" — from here up, NPS = OD in inches
The historical reason: NPS originally referred to the inner diameter of iron pipe with the thickest wall available in the late 1800s. As wall thicknesses changed, the OD was frozen so old fittings still worked, and the label stayed the same. That's why NPS and DN behave like part-numbers rather than measurements.
What "Schedule" means
For a given NPS, the outer diameter is fixed. The schedule number picks the wall thickness. Higher schedule → thicker wall → smaller inner diameter → higher pressure rating.
The schedule number is roughly proportional to 1000 × P / S, where P is design pressure (psi) and S is the allowable stress of the steel. Practically you treat it as a discrete code:
| Schedule | Aliases | Typical use |
|---|---|---|
| SCH 5 / 10 | 5S, 10S (stainless) | Low-pressure water, vent stacks, food/sanitary tube. |
| SCH 40 | STD (Standard Weight) | General service — plumbing, compressed air, low-pressure steam. |
| SCH 80 | XS (Extra-Strong) | Higher-pressure process lines, chemical service. |
| SCH 160 | — | High-pressure hydraulic and steam lines. |
| XXS | Double Extra-Strong | Very high-pressure or mechanical service. |
For NPS ≤ 10" the aliases line up almost exactly: STD == SCH 40 and XS == SCH 80. Above NPS 10" the two diverge — STD stays at 9.53 mm wall, while SCH 40 keeps thickening as the pipe grows.
The formulas the tool is using
The weight figure uses ρ = 7850 kg/m³ for carbon steel. For other materials, multiply by the ratio of densities — copper × 1.14, stainless × 1.02, PVC × 0.18. The volume figure ignores fittings and elbows; for a long straight run it's within 1% of the real answer.
Stainless steel and other related standards
- ASME B36.10M — Carbon and alloy welded / seamless steel pipe. The dimensions on this page.
- ASME B36.19M — Stainless steel pipe. Adds thin-wall "S" schedules (5S, 10S, 40S, 80S). For SCH 40S / 80S the wall thickness is identical to SCH 40 / 80 carbon steel up through NPS 12".
- EN 10220 — European equivalent for seamless and welded steel tube; uses outer diameter and wall thickness directly rather than NPS / schedule.
- JIS G 3454 / 3455 / 3456 — Japanese standards for carbon-steel pipes for piping (similar dimensional family).
- Copper Type K / L / M — Plumbing copper uses a completely different sizing convention. A 1/2" Type L copper has OD 5/8" — don't cross-reference.
Practical tips
OD is constant. If you're sizing a fitting or pipe support for a given NPS, OD is the only dimension you need — every schedule fits the same clamp.
Flow loss scales with the 4th power of ID. Going from SCH 40 to SCH 80 on a 2" line shrinks ID by 1.6 mm — a small change to the eye, but it cuts max flow capacity by roughly 7% at the same pressure drop. Match schedule to pressure, not flow.
For fluid volume on long runs the L/m figure adds up fast. A 100 m run of NPS 6" SCH 40 holds about 2,000 L of water — important for drain-down planning and chemical dosing.
Frequently asked questions
+What is the difference between NPS and DN?
NPS (Nominal Pipe Size) is the US/imperial label in inches; DN (Diameter Nominal) is the metric equivalent. They map one-to-one and refer to the same physical pipe — NPS 2" is identical to DN 50.
+Is NPS the actual outer diameter of the pipe?
No — for NPS 12" and smaller, the label does not match the real outer diameter. NPS 2" has an OD of 60.32 mm (≈ 2.37"). From NPS 14" upward, NPS equals OD in inches exactly.
+What does Schedule 40 mean?
Schedule 40 is a wall-thickness designation. For a given NPS, OD is fixed; the schedule picks how thick the wall is. SCH 40 is the most common general-service wall and is equivalent to STD (Standard Weight) up through NPS 10".
+How do I find inner diameter from NPS and schedule?
ID = OD − 2 × wall thickness. Pick the NPS to read the OD, then pick the schedule to read the wall — the tool computes ID for you in mm and inches.
+What is the weight of steel pipe per metre?
Weight per metre = π × (OD − wall) × wall × ρ, where ρ = 7850 kg/m³ for carbon steel. The calculator shows this value for the selected size and schedule; multiply by 1.02 for stainless, 1.14 for copper, 0.18 for PVC.
+How much water fits in a pipe per metre?
Volume per metre = π/4 × ID² (in metres), converted to litres. A 100 m run of NPS 6" SCH 40 holds about 2,000 L of water.