Whether you are an engineering student learning fluid dynamics, a professional sizing a water pump, or a technician managing an irrigation system, understanding how to accurately convert GPM to m³/hr is essential. Volume flow rate conversions can be tricky, especially when translating equipment specifications between US customary units and the metric system.
In this guide, we will break down the exact mathematical formulas, provide a quick reference table, and show you step-by-step how to convert US GPM to m³/hr (and vice versa) with absolute precision.
Quick Conversion Formula
To calculate cubic meters per hour, multiply your US GPM by the standard conversion factor:
The Core Conversion Formulas
To perform these calculations manually or program them into your own spreadsheets, you need the standard conversion factors.
1. Converting GPM to m³/h
To find the flow rate in cubic meters per hour, multiply your US gallons per minute by 0.2271247070524.
2. Converting m³/h to GPM
If you have a metric flow rate and need to switch back to US gallons per minute, you will multiply your cubic meters per hour by 4.4028675390625.
Why Do We Convert US GPM to CMH?
In many technical fields and international blueprints, you will see cubic meters per hour written as CMH, m3h, or meter cube per hour.
If you are purchasing equipment manufactured overseas, the factory might list the flow rate as m3/h, while your local building codes or project specifications require US GPM. Understanding that calculating gpm to cmh is the exact same process as convert gpm to m3/hr will save you a lot of confusion when reviewing spec sheets.
Step-by-Step Example: 20 GPM to m³/hr
Let’s look at a practical, real-world example. Suppose you are looking at a commercial water pump rated for a flow rate of 20 GPM, but your system engineer requested the capacity in metric units.
- Identify the starting value:
- Apply the exact conversion factor:
- Set up the calculation:
So, a flow rate of 20 GPM is equal to approximately 4.54 cubic meters per hour.
You can use our unit converter to convert GPM to m^3/hr and m^3 to GPM, online.
Quick Reference Conversion Table
For quick lookups in the field, here is a handy reference chart showing common gpm to cubic meter per hour conversions:
| Gallons Per Minute (US GPM) | Cubic Meters Per Hour (m³/h) |
| 1 GPM | 0.2271 m³/h |
| 5 GPM | 1.1356 m³/h |
| 10 GPM | 2.2712 m³/h |
| 20 GPM | 4.5425 m³/h |
| 50 GPM | 11.3562 m³/h |
| 100 GPM | 22.7125 m³/h |