Convert Liters/min to GPM: Formula & Calculator

This calculator converts a flow rate from liters per minute (L/min) to US gallons per minute (GPM). You enter the flow rate in L/min, and you get the equivalent in GPM instantly, along with the exact conversion factor used. The conversion is a simple multiplication: GPM = L/min × 0.264172.

Formula

The conversion from liters per minute to US gallons per minute uses a fixed volume ratio:

GPM = L/min × 0.264172

Where:

• L/min = flow rate in liters per minute (the value you input)
• GPM = flow rate in US gallons per minute (the result)
• 0.264172 = number of US gallons in one liter (exact: 1 L = 0.264172052 US gal)

Note that this uses the US liquid gallon (231 cubic inches), not the imperial gallon (277.42 cubic inches) used in the UK and some other countries. If you need imperial gallons, the factor is different: 1 L = 0.219969 imperial gallons.

Worked Example

Using the default value of 10 L/min:

1. Start with the flow rate: 10 L/min
2. Multiply by the conversion factor: 10 × 0.264172 = 2.64172
3. Round to two decimal places: 2.64 GPM

The calculator shows 2.64 GPM, matching the manual calculation.

Why Convert L/min to GPM?

Flow rate units vary by region and industry. Liters per minute is standard in most of the world (metric system), while gallons per minute is common in the United States for plumbing, irrigation, pool pumps, and industrial equipment. If you’re working with a pump, filter, or pipe that was manufactured in the US but you’re used to metric, or vice versa, you’ll need to convert between the two to compare specs or set controls correctly.

For example, a European-built water pump might state its capacity as 20 L/min, but a US-based installer needs to know that’s about 5.28 GPM to match it with US-standard pipes and fixtures. Similarly, a US pool pump rated at 30 GPM is roughly 113.6 L/min for someone using metric equipment.

How the Conversion Works

The conversion relies on the definition of the US gallon: exactly 231 cubic inches. One liter is defined as 1,000 cubic centimeters (or 0.001 cubic meters). When you convert between these two volume units, you get the constant 0.264172 gallons per liter. That constant never changes, so the conversion is always a simple multiplication.

Because it’s a linear conversion, you can also do it in reverse: to convert GPM to L/min, divide by 0.264172 (or multiply by 3.78541). The calculator only does one direction, but you can easily flip the formula if needed.

Common Mistakes and Misconceptions

• Using the wrong gallon: The biggest error is using the imperial gallon instead of the US gallon. The difference is about 20% (1 imperial gallon = 1.20095 US gallons). Always confirm which gallon your equipment or region uses.
• Confusing liters per second with liters per minute: Some flow meters display L/s. To convert L/s to GPM, first multiply by 60 to get L/min, then by 0.264172. Skipping the time conversion gives a result that’s 60 times too small.
• Rounding too early: If you round the conversion factor to 0.26, you’ll get a slightly off result. For most practical purposes, 0.264 is close enough, but for precise engineering, use 0.264172.
• Forgetting the “per minute” part: The conversion factor works only if both units are per minute. If you have liters per hour, convert to per minute first.

When to Use This Conversion

You’ll need this conversion in many real-world situations:

• Plumbing and irrigation: Matching pump flow rates to pipe sizes or sprinkler heads.
• Aquarium and pool equipment: Checking that a filter or pump’s flow rate meets the tank’s needs.
• Industrial processes: Comparing flow meters from different manufacturers.
• Automotive and machinery: Fuel pumps, coolant systems, hydraulic pumps.
• Home brewing or DIY projects: When following a US recipe or using a US-made pump.

In all these cases, the conversion is the same—just multiply the L/min value by 0.264172.

Limits of the Formula

This conversion is purely volumetric. It doesn’t account for fluid density, temperature, or pressure. For example, 10 L/min of water and 10 L/min of oil both convert to 2.64 GPM, even though their mass flow rates differ. If you need mass flow (e.g., kg/min or lb/min), you must multiply by the fluid’s density.

Also, the formula assumes a steady, incompressible flow. For gases at high pressure, the volumetric flow rate changes with pressure and temperature, so a simple unit conversion may not be sufficient—you might need to use standard conditions (STP) instead.

Frequently Asked Questions

How many GPM is 1 L/min?

1 L/min is equal to 0.264172 US GPM. So if you have a flow rate of 1 liter per minute, that’s about a quarter of a gallon per minute.

Is the conversion the same for imperial gallons?

No. The conversion factor for imperial gallons is 0.219969 (1 L = 0.219969 imperial gallons). That’s about 17% less than the US gallon factor. Always check which gallon your country or industry uses.

How do I convert GPM to L/min?

Divide the GPM value by 0.264172, or multiply by 3.78541. For example, 5 GPM × 3.78541 = 18.93 L/min.

What is the difference between US and imperial gallons?

The US gallon is defined as 231 cubic inches (about 3.785 liters). The imperial gallon is defined as 4.54609 liters. The imperial gallon is about 20% larger than the US gallon.

Why do some countries use L/min and others GPM?

It’s a matter of measurement systems. Most countries use the metric system (liters, meters), while the US still commonly uses imperial/customary units (gallons, feet). This conversion is needed whenever equipment from different regions is used together.

Can I use this for gases?

Yes, for volumetric flow of gases at the same temperature and pressure. But if pressure or temperature changes, the gas volume changes, so the conversion may not reflect the actual mass flow. For accurate gas flow, use standard conditions (e.g., SLPM or SCFM).

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in lpm | Flow rate | L/min | 10 | 0
out gpm | Flow rate | GPM | lpm * 0.264172 | 2