Flow Unit Converter

Spec sheets and pump curves never agree on units. One manufacturer quotes m³/h, another GPM, a third MGD, and the process engineer is left converting on a calculator mid-meeting. This converter settles it: enter a value in any of the common water and wastewater flow units and read it in all the others at once.

Convert flow unit units

Value

From

Why flow units never match

Pump and flowmeter catalogues mix metric and imperial freely, and add at least three volume bases — cubic metres, litres and US gallons — on top of the time base of seconds, minutes and days. A single treatment train can quote m³/h for the raw intake, L/s for a dosing pump and MGD for the whole plant, so the same physical flow appears as three different numbers.

Converting between them is pure arithmetic with no physical assumption, which is why a converter can be exact. The only thing to watch is which gallon — this tool uses the US gallon (231 in³, 3.785 L); the imperial gallon is 4.546 L and must not be substituted.

Where each unit shows up

m³/h and L/s dominate equipment nameplates and pipe sizing in metric markets. US gpm and MGD are the language of North American water and wastewater specifications, with MGD used for whole-plant and permit flows. ft³/min (CFM) appears in aeration and blower data, where it describes air, not water — but the same converter handles it.

Complete conversion reference

Convert 1 unit to	m³/h	m³/d	m³/min	L/s	L/min	US gpm	ft³/min	US MGD
1 m³/h	1	24	0.0166667	0.277778	16.6667	4.40287	0.588578	0.00634013
1 m³/d	0.0416667	1	0.000694444	0.0115741	0.694444	0.183453	0.0245241	0.000264172
1 m³/min	60	1440	1	16.6667	1000	264.172	35.3147	0.380408
1 L/s	3.6	86.4	0.06	1	60	15.8503	2.11888	0.0228245
1 L/min	0.06	1.44	0.001	0.0166667	1	0.264172	0.0353147	0.000380408
1 US gpm	0.227125	5.45099	0.00378541	0.0630902	3.78541	1	0.133681	0.00144
1 ft³/min	1.69901	40.7763	0.0283168	0.471947	28.3168	7.48052	1	0.0107719
1 US MGD	157.725	3785.41	2.62876	43.8126	2628.76	694.444	92.8337	1

Instruments for this measurement

SE10A

Electromagnetic flowmeter, 24V DC

Lining PTFE/PU · DN10–1200

SV21

Vortex flowmeter, steam / gas / liquid

DN15–300 · no moving parts

SG61

Coriolis mass flowmeter

Direct mass & density

Flowmeter Selection Guide

Vortex, magnetic, thermal & DP

Choose by fluid, not brand

Flowmeter selection: fluid first

Application-led selection insight

Wet-side-first method

Models shown are representative families, not a complete catalogue. Send us your application, water analysis and installation constraints and we will match instruments to it.

Frequently asked

How many US gallons are in a cubic metre?

Exactly 264.172 US gallons (1 m³ = 1000 L; 1 US gallon = 3.78541 L). This converter uses the US gallon throughout; the imperial gallon is 4.546 L and is not used here.

What is 1 MGD in metric units?

One million US gallons per day equals about 43.81 L/s, 157.7 m³/h or 3785 m³/day. MGD is the standard whole-plant flow unit in US water and wastewater practice.

Why does my pump curve use gpm but the pipe uses m³/h?

Different conventions in the same document are normal: gpm is traditional for pump performance in imperial markets, while m³/h is the metric pipe-sizing unit. Convert with this tool rather than mixing them in one calculation.

Is CFM the same as GPM?

No. CFM (ft³/min) measures volume per minute in cubic feet, while GPM measures US gallons per minute. They are not interchangeable; CFM is common for air and blower flows, GPM for liquids.

This page performs exact unit arithmetic with no physical assumption beyond the stated reference (for example mH₂O assumes water near 4 °C, and pH follows its logarithmic definition). It is a working aid, not a substitute for the measurement method named in your permit.