Pipe Flow Rate Calculator Reference Values

Calculate pipe flow rate in gpm from inside diameter and flow velocity.

Author

Dr. Amara Osei

Plumbing editorial contributor

Ghanaian computational linguist with a PhD from MIT, specializing in NLP for low-resource African languages

Reviewed for accuracy by

Prof. Zara Khan

Plumbing content reviewer

Pakistani-British education researcher at Cambridge, evaluating digital literacy programs in South Asian rural schools

Last updatedFebruary 22, 2026

PublishedFebruary 22, 2026

Reference Value Index

This page lists 48 reference values for quick browsing and lookup.

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All Reference Values

Reference Table

Pipe Flow Rate Calculator reference values
Scenario	Flow (gpm)	Flow (cfs)	Flow (L/min)
0.5 in pipe at 2 ft/s	1.22 gpm	0.0027	4.6
0.5 in pipe at 3 ft/s	1.84 gpm	0.0041	7
0.5 in pipe at 4 ft/s	2.45 gpm	0.0055	9.3
0.5 in pipe at 5 ft/s	3.06 gpm	0.0068	11.6
0.5 in pipe at 6 ft/s	3.67 gpm	0.0082	13.9
0.5 in pipe at 8 ft/s	4.9 gpm	0.0109	18.5
0.75 in pipe at 2 ft/s	2.75 gpm	0.0061	10.4
0.75 in pipe at 3 ft/s	4.13 gpm	0.0092	15.6
0.75 in pipe at 4 ft/s	5.51 gpm	0.0123	20.9
0.75 in pipe at 5 ft/s	6.88 gpm	0.0153	26.1
0.75 in pipe at 6 ft/s	8.26 gpm	0.0184	31.3
0.75 in pipe at 8 ft/s	11.02 gpm	0.0245	41.7
1 in pipe at 2 ft/s	4.9 gpm	0.0109	18.5
1 in pipe at 3 ft/s	7.34 gpm	0.0164	27.8
1 in pipe at 4 ft/s	9.79 gpm	0.0218	37.1
1 in pipe at 5 ft/s	12.24 gpm	0.0273	46.3
1 in pipe at 6 ft/s	14.69 gpm	0.0327	55.6
1 in pipe at 8 ft/s	19.58 gpm	0.0436	74.1
1.25 in pipe at 2 ft/s	7.65 gpm	0.017	29
1.25 in pipe at 3 ft/s	11.47 gpm	0.0256	43.4
1.25 in pipe at 4 ft/s	15.3 gpm	0.0341	57.9
1.25 in pipe at 5 ft/s	19.12 gpm	0.0426	72.4
1.25 in pipe at 6 ft/s	22.95 gpm	0.0511	86.9
1.25 in pipe at 8 ft/s	30.6 gpm	0.0682	115.8
1.5 in pipe at 2 ft/s	11.02 gpm	0.0245	41.7
1.5 in pipe at 3 ft/s	16.52 gpm	0.0368	62.6
1.5 in pipe at 4 ft/s	22.03 gpm	0.0491	83.4
1.5 in pipe at 5 ft/s	27.54 gpm	0.0614	104.3
1.5 in pipe at 6 ft/s	33.05 gpm	0.0736	125.1
1.5 in pipe at 8 ft/s	44.06 gpm	0.0982	166.8
2 in pipe at 2 ft/s	19.58 gpm	0.0436	74.1
2 in pipe at 3 ft/s	29.38 gpm	0.0654	111.2
2 in pipe at 4 ft/s	39.17 gpm	0.0873	148.3
2 in pipe at 5 ft/s	48.96 gpm	0.1091	185.3
2 in pipe at 6 ft/s	58.75 gpm	0.1309	222.4
2 in pipe at 8 ft/s	78.34 gpm	0.1745	296.5
3 in pipe at 2 ft/s	44.06 gpm	0.0982	166.8
3 in pipe at 3 ft/s	66.1 gpm	0.1473	250.2
3 in pipe at 4 ft/s	88.13 gpm	0.1963	333.6
3 in pipe at 5 ft/s	110.16 gpm	0.2454	417
3 in pipe at 6 ft/s	132.19 gpm	0.2945	500.4
3 in pipe at 8 ft/s	176.26 gpm	0.3927	667.2
4 in pipe at 2 ft/s	78.34 gpm	0.1745	296.5
4 in pipe at 3 ft/s	117.5 gpm	0.2618	444.8
4 in pipe at 4 ft/s	156.67 gpm	0.3491	593.1
4 in pipe at 5 ft/s	195.84 gpm	0.4363	741.3
4 in pipe at 6 ft/s	235.01 gpm	0.5236	889.6
4 in pipe at 8 ft/s	313.34 gpm	0.6981	1,186.1

Frequently Asked Questions

Frequently asked questions for Pipe Flow Rate Calculator and its reference values.

What formula is used for pipe flow rate?

Flow is calculated as Q = A × v, where A is pipe cross-sectional area and v is flow velocity.

How do you convert cfs to gpm?

Multiply cubic feet per second by 448.831 to get gallons per minute.

Can I use nominal pipe size as inside diameter?

For better accuracy, use actual inside diameter. Nominal size and wall thickness vary by material and schedule.

What velocity range is typical in plumbing systems?

Many domestic systems target moderate velocities to limit noise and pressure loss, often around 2 to 8 ft/s depending on application.

Methodology and Review

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