How do I convert GPM to LPM?

Multiply GPM by 3.78541. For example, 5 GPM × 3.78541 = 18.93 LPM. To convert LPM to GPM, divide by 3.78541 (or multiply by 0.264172).

What is a good water flow rate for a house?

A residential main line typically provides 10–25 GPM (38–95 LPM). Individual fixtures need 1.5–3 GPM. Pipe sizing, water pressure, and distance from the meter all affect available flow.

What does CFM measure?

CFM (cubic feet per minute) measures the volume of air flowing per minute. It's the standard unit for HVAC ductwork, ventilation fans, and air compressors in the US. Metric equivalent is m³/h or L/s.

How is flow rate related to pipe size?

Flow rate, pipe diameter, and velocity are related: Q = A × v (flow = cross-sectional area × velocity). A larger pipe at the same velocity carries more flow. Pipe sizing charts use flow rate and acceptable velocity to determine the needed diameter.

What is the difference between flow rate and flow velocity?

Flow rate (GPM, LPM) is the volume per time. Velocity (ft/s, m/s) is the speed of the fluid. They're related by pipe area: velocity = flow rate / pipe area. The same flow rate through a smaller pipe means higher velocity.

Can I convert between liquid and air flow units?

While both are volumetric flow rates, comparing liquid GPM to air CFM directly can be misleading because air is compressible and much less dense. The conversion math is valid, but the practical context differs. 1 CFM air has far less mass than 1 GPM water.

Flow Rate Converter

Convert flow rates between GPM, LPM, cubic meters per hour, CFM, and liters per second. Uses the exact factor 1 GPM = 3.78541 LPM.

From Unit

To Unit

Flow Rate

Duration (minutes)

Pipe Diameter (inches)

Precision

Converted Flow

37.85 L/min

10 GPM converted to Liters/min

Base Rate (L/min)

37.85 L/min

Standard liters per minute used as conversion base

Conversion Factor

3.79

1 GPM = 3.79 L/min

Volume in 60 min

2,271.25 L

Total volume: 600.00 gal / 2.27 m³

Pipe Velocity

0.31 m/s

Flow speed through a 2" pipe (1.02 ft/s)

Total Gallons

600.00

US gallons produced over 60 minutes

All Unit Conversions

Unit	Value	Scale
GPM	10.00
GPH	600.00
L/min	37.85
L/h	2,271.25
L/s	0.63
m³/h	2.27
m³/s	0.00
CFM	1.34
CFS	0.02
IGPM	8.33

Pipe Velocity Guide

Application	Typical Velocity	Your Flow
Residential plumbing	0.5–1.5 m/s
Commercial piping	1.0–2.5 m/s
Fire protection	2.0–4.0 m/s
Industrial process	1.5–3.0 m/s

Planning notes, formulas, and examples

About the Flow Rate Converter

The Flow Rate Converter converts between gallons per minute (GPM), liters per minute (LPM), liters per second (L/s), cubic meters per hour (m³/h), and cubic feet per minute (CFM). These are the standard volumetric flow rate units used in plumbing, HVAC, industrial processes, and water treatment.

Flow rate measures the volume of fluid passing through a point per unit of time. It's critical for sizing pipes, pumps, valves, and HVAC ductwork. The US uses GPM for liquid and CFM for air. Metric systems use LPM, L/s, or m³/h depending on the application and scale.

The core liquid conversion is 1 GPM = 3.78541 LPM (based on 1 US gallon = 3.78541 liters). For air flow, 1 CFM = 28.3168 LPM. This converter handles both liquid and gas flow units for cross-system convenience.

When This Page Helps

Plumbers, HVAC technicians, and process engineers regularly convert between US and metric flow rate units. It returns the converted value across the common volumetric flow rate units used in field work and design.

How to Use the Inputs

Select the flow rate unit you are converting from.
Enter the flow rate value.
View equivalents in all other supported units.
Use GPM for US plumbing and LPM for metric water systems.
Use CFM for HVAC air flow and m³/h for industrial processes.

Formula used

1 GPM = 3.78541 LPM = 0.0630902 L/s = 0.227125 m³/h
1 CFM = 28.3168 LPM = 0.471947 L/s = 1.69901 m³/h
1 m³/h = 4.40287 GPM = 16.6667 LPM = 0.27778 L/s

Example Calculation

Result: 37.85 LPM / 2.27 m³/h

10 GPM × 3.78541 = 37.85 LPM. 10 GPM × 0.227125 = 2.27 m³/h. 10 GPM is a typical flow rate for a residential main water line or a medium-sized pump.

Tips & Best Practices

A typical kitchen faucet flows at 1.5–2.2 GPM (5.7–8.3 LPM).
A shower head: 2.0–2.5 GPM. A garden hose: 5–10 GPM.
Low-flow fixtures are rated at 1.5 GPM or less for water conservation.
HVAC systems measure air flow in CFM: a residential system might move 400 1,200 CFM.
Industrial processes often use m³/h for large-scale liquid and gas flows.

Flow Rate in Plumbing

Residential plumbing design is based on flow rates. The main water line is sized for peak demand (multiple fixtures running simultaneously). Pipe sizes range from 3/4" (10–15 GPM) to 1" (20–30 GPM) for homes. Commercial buildings use larger pipes and higher flow rates.

Flow Rate in HVAC

Air conditioning systems move air through ducts measured in CFM. A typical residential system moves 400 CFM per ton of cooling. Duct sizing balances flow rate against velocity to minimize noise and pressure drop. Bathroom exhaust fans are rated at 50–150 CFM.

Industrial Flow Measurement

Industrial processes use various flow meters: magnetic, ultrasonic, Coriolis, turbine, and differential pressure. Flow rates range from mL/min in lab settings to thousands of m³/h in water treatment. Accurate flow measurement is critical for process control, billing, and safety.

Sources & Methodology

Last updated: February 8, 2026

Frequently Asked Questions

Multiply GPM by 3.78541. For example, 5 GPM × 3.78541 = 18.93 LPM. To convert LPM to GPM, divide by 3.78541 (or multiply by 0.264172).