Flow rate converter — l/s, m³/h, GPM and CFM

Pump curves in m³/h, plumbing figures in litres per minute, American specs in GPM, ventilation in CFM. Seven flow units in one place, and branches can be added together.

How to use it

1
Type into any row — say l/s or m³/h. The results appear immediately, no button needed.
2
Need a combined figure? Fill in two rows, for example l/s and GPM, and they are added together before converting.
3
Set how many digits you want (4–12) and click a result to copy the plain number.

Exact conversion factors

These are the definitions the calculator uses. Nothing here is rounded for convenience — where a value is exact by definition, it says so.

1 l/s = 3.6 m³/h = 60 l/min = 15.8503231 GPM
1 m³/h = 0.277777778 l/s = 4.40286754 GPM
1 US GPM = 3.785411784 l/min = 0.0630901964 l/s
1 CFM = 1.6990108 m³/h = 0.4719474432 l/s

Formulal/s = m³/h ÷ 3.6 · l/s = GPM × 0.0630901964 · l/s = CFM × 0.4719474432

Flow rate conversion table — every unit

One of each unit, converted into the three units people ask for most.

Unit	l/s	m³/h	GPM
1 l/s	1 l/s	3.6 m³/h	15.8503 GPM
1 l/min	0.0166667 l/s	0.06 m³/h	0.264172 GPM
1 l/h	0.000277778 l/s	0.001 m³/h	0.00440287 GPM
1 m³/s	1 000 l/s	3 600 m³/h	15 850.3 GPM
1 m³/h	0.277778 l/s	1 m³/h	4.40287 GPM
1 GPM	0.0630902 l/s	0.227125 m³/h	1 GPM
1 CFM	0.471947 l/s	1.69901 m³/h	7.48052 GPM

l/s → m³/h, GPM — quick values

l/s	m³/h	GPM
0.5 l/s	1.8 m³/h	7.92516 GPM
1 l/s	3.6 m³/h	15.8503 GPM
2 l/s	7.2 m³/h	31.7006 GPM
3 l/s	10.8 m³/h	47.551 GPM
5 l/s	18 m³/h	79.2516 GPM
10 l/s	36 m³/h	158.503 GPM
20 l/s	72 m³/h	317.006 GPM
25 l/s	90 m³/h	396.258 GPM
50 l/s	180 m³/h	792.516 GPM
100 l/s	360 m³/h	1 585.03 GPM
250 l/s	900 m³/h	3 962.58 GPM
1 000 l/s	3 600 m³/h	15 850.3 GPM

How this converter works

Pump and fan catalogues change units at national borders. A pump rated 20 m³/h delivers 5.56 l/s or 88.06 GPM; a fan rated 500 CFM moves 236 l/s or 849.5 m³/h. Comparing two suppliers usually means converting one of them first.

Because the rows are summed, you can combine branches of a system directly: enter each branch in whatever unit its datasheet uses and read the combined flow at the bottom. That is quicker than normalising every figure by hand before adding.

Notes and abbreviations

1 l/s = 3.6 m³/h = 60 l/min = 15.85 GPM
GPM here is the US gallon per minute (3.785 l), not the imperial one
CFM — cubic feet per minute, the standard unit for ventilation and compressors

Questions

How many litres per minute is 1 m³/h?

16.667 l/min, or 0.2778 l/s.

Is GPM US or imperial here?

US. An imperial GPM is 20.1 percent larger — convert via the volume page if your source is British.

Can I total several pipe branches?

Yes. Fill in one row per branch and the outputs show the sum in every unit.