Pipe Size Chart(NPS, DN, Schedule, OD & ID)

A clear, printable pipe size chart that translates nominal sizes into real dimensions for fast, reliable field decisions. Covers NPS 1/8 to 24 with Schedules 5 through XXS.

NPS & DNDual standards
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SchedulesWall thickness & ID
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Residential Plumbing • 1/2 → 8 • A4

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Pipe Size Chart

Standard: NPS • Range: 1/2 - 8 • A4

NPSDNODScheduleWallIDWeight
1/2DN 150.840" / 21.3mmSCH 400.109" / 2.77mm0.622" / 15.76mm0.85 lb/ft / 1.27 kg/m
1/2DN 150.840" / 21.3mmSCH 800.147" / 3.73mm0.546" / 13.84mm1.09 lb/ft / 1.62 kg/m
3/4DN 201.050" / 26.7mmSCH 400.113" / 2.87mm0.824" / 20.96mm1.13 lb/ft / 1.69 kg/m
3/4DN 201.050" / 26.7mmSCH 800.154" / 3.91mm0.742" / 18.88mm1.48 lb/ft / 2.20 kg/m
1DN 251.315" / 33.4mmSCH 400.133" / 3.38mm1.049" / 26.64mm1.68 lb/ft / 2.50 kg/m
1DN 251.315" / 33.4mmSCH 800.179" / 4.55mm0.957" / 24.30mm2.17 lb/ft / 3.24 kg/m
1-1/4DN 321.660" / 42.2mmSCH 400.140" / 3.56mm1.380" / 35.08mm2.27 lb/ft / 3.39 kg/m
1-1/4DN 321.660" / 42.2mmSCH 800.191" / 4.85mm1.278" / 32.50mm3.00 lb/ft / 4.47 kg/m
1-1/2DN 401.900" / 48.3mmSCH 400.145" / 3.68mm1.610" / 40.94mm2.72 lb/ft / 4.05 kg/m
1-1/2DN 401.900" / 48.3mmSCH 800.200" / 5.08mm1.500" / 38.14mm3.63 lb/ft / 5.41 kg/m
2DN 502.375" / 60.3mmSCH 400.154" / 3.91mm2.067" / 52.48mm3.66 lb/ft / 5.44 kg/m
2DN 502.375" / 60.3mmSCH 800.218" / 5.54mm1.939" / 49.22mm5.03 lb/ft / 7.48 kg/m
2-1/2DN 652.875" / 73.0mmSCH 400.203" / 5.16mm2.469" / 62.68mm5.80 lb/ft / 8.63 kg/m
2-1/2DN 652.875" / 73.0mmSCH 800.276" / 7.01mm2.323" / 58.98mm7.67 lb/ft / 11.41 kg/m
3DN 803.500" / 88.9mmSCH 400.216" / 5.49mm3.068" / 77.92mm7.58 lb/ft / 11.29 kg/m
3DN 803.500" / 88.9mmSCH 800.300" / 7.62mm2.900" / 73.66mm10.26 lb/ft / 15.27 kg/m
3-1/2DN 904.000" / 101.6mmSCH 400.226" / 5.74mm3.548" / 90.12mm9.12 lb/ft / 13.57 kg/m
3-1/2DN 904.000" / 101.6mmSCH 800.318" / 8.08mm3.364" / 85.44mm12.52 lb/ft / 18.63 kg/m
4DN 1004.500" / 114.3mmSCH 400.237" / 6.02mm4.026" / 102.26mm10.80 lb/ft / 16.07 kg/m
4DN 1004.500" / 114.3mmSCH 800.337" / 8.56mm3.826" / 97.18mm15.00 lb/ft / 22.32 kg/m
5DN 1255.563" / 141.3mmSCH 400.258" / 6.55mm5.047" / 128.20mm14.63 lb/ft / 21.77 kg/m
5DN 1255.563" / 141.3mmSCH 800.375" / 9.53mm4.813" / 122.24mm20.80 lb/ft / 30.97 kg/m
6DN 1506.625" / 168.3mmSCH 400.280" / 7.11mm6.065" / 154.08mm18.99 lb/ft / 28.26 kg/m
6DN 1506.625" / 168.3mmSCH 800.432" / 10.97mm5.761" / 146.36mm28.60 lb/ft / 42.56 kg/m
8DN 2008.625" / 219.1mmSCH 400.322" / 8.18mm7.981" / 202.74mm28.58 lb/ft / 42.55 kg/m
8DN 2008.625" / 219.1mmSCH 800.500" / 12.70mm7.625" / 193.70mm43.43 lb/ft / 64.64 kg/m

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File Details

Rows

26

Range

1/2 → 8 • A4

PDF FILE SIZE

≈0KB

Quality

300 DPI

How to Read Pipe Sizes

Navigating the difference between what it's called and what it measures.

Nominal vs Actual

Understand that NPS (Nominal Pipe Size) is a label, not the actual diameter. For sizes 1/8 to 12, OD is larger than NPS. From 14 up, OD matches NPS.

Check the Schedule

Schedule (SCH 40, 80, etc.) defines the wall thickness. As Schedule increases, wall gets thicker and ID gets smaller, but OD stays constant.

NPS to DN Conversion

Use the chart to convert between Inch-based NPS and Metric DN (Diameter Nominal). Example: NPS 2 = DN 50.

Common Applications

Where these standards apply in the real world.

🚿

Plumbing & Building

Choose pipe for supply, drainage, and risers. Verify OD for clamps and wall penetrations.

  • •NPS 1/2 to 4 common sizes
  • •Schedule 40 for most water lines
  • •DWV systems
🏭

Industrial & Process

Match wall thickness to pressure requirements. Heavy wall (SCH 80/160) for high pressure or corrosive fluids.

  • •Process piping systems
  • •High-pressure steam
  • •Chemical transport
❄️

HVAC & Mechanical

Sizing for chilled water, heating hot water, and gas lines. Critical for flow rate and insulation fit.

  • •Hydronic heating loops
  • •Gas piping (Black Iron)
  • •Insulation clearance

Pipe Standards Explained

NPS, DN, and Schedule: Decoding the terminology.

ASME B36.10NPS (Nominal Pipe Size)

North American standard using inches. Key takeaway: For sizes 1/8" to 12", the NPS does NOT equal the Outside Diameter (OD). For 14" and larger, NPS = OD.

NPS 1/2 → OD 0.840"

NPS 2 → OD 2.375"

NPS 14 → OD 14.000"

ISODN (Diamètre Nominal)

Metric designation used internationally. It is a loose reference to the internal diameter in millimeters, but like NPS, it is a name, not an exact measure.

DN 15 ≈ NPS 1/2

DN 50 ≈ NPS 2

DN 350 ≈ NPS 14

Selection Tips for Real Projects

Avoid common pitfalls when ordering or installing pipe.

1

Confirm OD for Fittings

Fittings, hangers, and supports are sized by OD. Never assume NPS matches the ruler.

2

Check Pressure Ratings

Higher schedule = thicker wall = higher pressure rating, but also heavier weight and smaller flow area.

3

Insulation Clearance

When running multiple pipes, calculate spacing based on OD + Insulation thickness, not just nominal size.

4

Thread Standards

NPT (Tapered) is standard for threaded pipe in US. Ensure valves and fittings match.

Related Workshop Charts

Essential references for mechanical and shop work.

Bolt SizesWorkshop
SizePitch/TPIHead
M30.55.5
M40.77.0
M50.88.0
M61.010.0
M81.2513.0
1/4"207/16"
5/16"181/2"
3/8"169/16"

Bolt & Screw Sizes

Metric and imperial bolt, screw, and thread pitch reference.

View chart
Drill Bit SizesWorkshop chart
NumberFractionDecimal (in)Millimeters
#80—0.01350.34
#50—0.07001.78
#521/16"0.06251.59
#413/32"0.09382.38
#225/32"0.15623.97
#113/16"0.18754.76
#713/64"0.20315.16
——0.25706.53
—3/8"0.37509.53
—1/2"0.500012.70

Drill Bit Sizes

Numbered, lettered, metric, and fractional drill bit reference.

View chart
Fraction → DecimalEducational
FractionDecimalPercent
1/640.01561.56%
1/320.03133.13%
1/160.06256.25%
1/80.125012.5%
3/160.187518.8%
1/40.250025%
5/160.312531.3%
3/80.375037.5%
1/20.500050%
3/40.750075%

Fraction to Decimal

Fractions from 1/64 to whole numbers for math education and precision cutting.

View chart
PSI → BarEngineering
PSIBarkPa
100.6969
201.38138
302.07207
322.21221
352.41241
402.76276
503.45345
604.14414
805.52552
1006.89689

PSI to Bar Chart

Professional PSI to Bar conversion table for tires, hydraulics, and diving. Includes kPa and atm.

View chart

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Frequently Asked Questions

Common questions about pipe sizing and standards.

Why doesn't NPS match the actual diameter?
NPS (Nominal Pipe Size) is a historical designation. Originally, the ID was close to the nominal size for standard wall thickness. As manufacturing improved and wall thicknesses were standardized, the OD was fixed to ensure fitting compatibility, while the ID varies with schedule.
Does schedule affect the Outside Diameter (OD)?
No. For a given NPS, the Outside Diameter (OD) is always the same, regardless of the schedule. The schedule changes the Wall Thickness, which in turn changes the Inside Diameter (ID).
What is the difference between SCH 40 and SCH 80?
SCH 80 has a thicker wall than SCH 40. This means SCH 80 can handle higher pressures but has a smaller internal flow area (ID) and is heavier and more expensive.
Is DN an exact millimeter value?
No, DN (Diameter Nominal) is a dimensionless designation. For example, DN 25 corresponds to 33.4mm OD, not 25mm. It is just a name for the size class.
Which schedule should I choose?
It depends on the pressure, temperature, and corrosion allowance required for your system. Schedule 40 is standard for most residential water and gas lines. Schedule 80 is used for high pressure or industrial applications.
What is 'STD' and 'XS'?
STD (Standard) often matches SCH 40 for sizes up to NPS 10. XS (Extra Strong) often matches SCH 80 for sizes up to NPS 8. Check the chart for exact matches.
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