Standard Pipe Diameter and Flow Rate Tables

1. PIPE DIAMETERS AND LOSS CALCULATION FOR LIQUID FLOW (PUMP INSTALLATIONS)

This detailed set of tables includes the most commonly used Nominal Diameter (DN) series in the piping industry. Pipe flow rate (Capacity) and friction loss (mWC/100m) values are calculated based on material type and internal surface roughness. This ensures the most accurate decisions during project selection.

1.1. Steel Pipes (High Roughness - DIN 2440 / Welded Black Steel)

Nominal Diameter (DN)	Outer Diameter (mm)	Wall Thickness (mm) (Approx.)	Inner Diameter (mm) (Approx.)	Ideal Velocity (1.5 m/s) Flow (m³/h)	Max. Velocity (2.5 m/s) Flow (m³/h)	Approx. Friction Loss (mWC/100m) @ 1.5 m/s
10	17.2	2.35	12.5	0.79	1.32	2.25
15	21.3	2.35	16.6	1.25	2.08	1.75
20	26.9	2.65	21.6	2.02	3.37	1.55
25	33.7	3.25	27.2	3.24	5.40	1.40
32	42.4	3.25	35.9	5.43	9.05	1.25
40	48.3	3.25	41.8	7.40	12.33	1.20
50	60.3	3.65	53.0	12.50	20.83	1.15
65	76.1	3.65	68.8	20.25	33.75	1.05
80	88.9	4.05	80.8	29.58	49.30	1.00
100	114.3	4.50	105.3	49.70	82.83	0.95
150	168.3	4.50	159.3	114.30	190.50	0.85
200	219.1	5.90	207.3	189.50	315.80	0.75

1.2. Plastic Pipes (Very Low Roughness - PPRC / PVC / U-PVC)

Nominal Diameter (DN)	Outer Diameter (mm)	Inner Diameter (mm) (Approx.)	Ideal Velocity (1.5 m/s) Flow (m³/h)	Max. Velocity (2.5 m/s) Flow (m³/h)	Approx. Friction Loss (mWC/100m) @ 1.5 m/s
10	16	13.0	0.86	1.43	1.80
15	20	16.6	1.25	2.08	1.35
20	25	21.0	1.87	3.12	1.15
25	32	27.2	3.24	5.40	1.00
32	40	33.8	4.84	8.06	0.90
40	50	42.6	7.64	12.73	0.85
50	63	53.0	11.90	19.83	0.80
65	75	65.8	18.06	30.10	0.70
80	90	81.6	27.26	45.43	0.65
100	110	103.6	47.78	79.63	0.60
150	160	154.6	103.50	172.50	0.55
200	225	205.6	187.00	311.66	0.50

1.3. Stainless Steel Pipes (Clean Surface - 304 / 316)

Nominal Diameter (DN)	Outer Diameter (mm)	Inner Diameter (mm) (Approx.)	Ideal Velocity (1.5 m/s) Flow (m³/h)	Max. Velocity (2.5 m/s) Flow (m³/h)	Approx. Friction Loss (mWC/100m) @ 1.5 m/s
15	21.3	17.3	1.30	2.17	1.50
25	33.7	29.7	3.73	6.22	1.25
50	60.3	55.3	12.87	21.45	0.95
80	88.9	84.9	30.65	51.08	0.85
100	114.3	108.3	50.91	84.85	0.80
150	168.3	163.3	119.50	199.16	0.70
200	219.1	215.1	208.68	347.80	0.65

2. PIPE DIAMETERS AND LOSS CALCULATION FOR GAS FLOW (COMPRESSED AIR)

In compressed air systems, the main criterion is pressure drop. This table shows nominal flow rates at an operating pressure of 7 bar and a temperature of 20°C, along with the associated pressure losses.

2.1. Compressed Air Flow Table (m³/h) and Pressure Loss (DN 15 to DN 150)

Velocity (m/s)	DN 15	DN 25	DN 40	DN 65	DN 100	DN 150	Ex: Pressure Loss (bar/100m) @ 5 m/s
3	2.16	6.12	14.76	39.24	92.52	202.32	0.005
4	2.88	8.28	19.44	52.56	123.12	269.64	0.009
5	3.60	10.08	24.48	65.52	154.08	336.96	0.014
6	4.32	12.24	29.16	78.48	184.68	403.2	0.020
8	5.76	16.2	38.88	104.76	246.6	540.0	0.035

2.2. Value of Free Air Volume Under Pressure (dm³) (Ideal Gas Law)

Shows the equivalent volume of the compressor's FAD (Free Air Delivery) capacity under the operating pressure in the pipeline. This calculation is based on the following simple formula.

Volume (Under Pressure) = Volume (Free Air) / (Operating Pressure (bar) + 1)
Vpressure = Vfree / (Pbar + 1)

Free Air Volume (dm³)	Volume at 4 bar (dm³)	Volume at 6 bar (dm³)	Volume at 8 bar (dm³)
5	1.0	0.71	0.56
10	2.0	1.43	1.11
25	5.0	3.57	2.78
50	10.0	7.14	5.56
100	20.0	14.29	11.11
200	40.0	28.57	22.22
500	100.0	71.43	55.56

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