Flow Rate Unit Converter - m³/s, L/min, GPM, CFM

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Formulas

Examples

Guide

Flow Rate Converter

Engineering Note: This converter handles both volumetric flow rates (volume/time) and mass flow rates (mass/time). For mass flow conversions, fluid density is considered based on selected fluid type.

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Mass Flow

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Common Flow Rate Units

Volumetric Flow Rate Units

Cubic meter per second

m³/s

SI unit for volumetric flow rate. Used in engineering calculations.

Liters per minute

L/min

Common for HVAC and plumbing applications. Easy to visualize.

Gallons per minute

GPM

Standard in US plumbing and water systems. Widely used measure.

Cubic feet per minute

CFM

HVAC and ventilation standard. Used for air flow measurements.

Mass Flow Rate Units

Kilogram per second

kg/s

SI unit for mass flow rate. Used in process engineering.

Tonne per hour

t/h

Heavy industry standard. Used for bulk material handling.

Volumetric Flow Rate Conversion Table

Unit	Symbol	1 m³/s equals	Common usage
Cubic meter per second	m³/s	1	SI unit, engineering
Liter per minute	L/min	60,000	HVAC, plumbing
Liter per second	L/s	1,000	Small pumps
Gallon per minute	GPM	15,850	US plumbing
Cubic feet per minute	CFM	2,119	HVAC, ventilation
Cubic meter per hour	m³/h	3,600	Industrial

Mass Flow Rate Conversion Table

Unit	Symbol	1 kg/s equals	Common usage
Kilogram per second	kg/s	1	SI unit, engineering
Kilogram per hour	kg/h	3,600	Process industry
Pound per second	lb/s	2.205	US engineering
Tonne per hour	t/h	3.6	Heavy industry

Flow Rate Formulas & Conversions

Basic Flow Rate Relationship

Mass Flow = Volume Flow × Density

ṁ = Q × ρ
ṁ = Mass flow rate (kg/s)
Q = Volume flow rate (m³/s)
ρ = Fluid density (kg/m³)

Volumetric Flow Conversions

m³/s × 60,000 = L/min

GPM × 6.309×10⁻⁵ = m³/s

CFM × 4.719×10⁻⁴ = m³/s

m³/h ÷ 3600 = m³/s

Mass Flow Conversions

kg/s × 3600 = kg/h

lb/s × 0.4536 = kg/s

t/h ÷ 3.6 = kg/s

Pipe Flow Velocity

Q = A × v

Q: Flow rate (m³/s)
A: Cross-sectional area (m²)
v: Average velocity (m/s)

Common Fluid Densities

Fluid	Density (kg/m³)	Temperature	Applications
Water	1000	20°C	Plumbing, cooling systems
Air	1.225	15°C, 1 atm	HVAC, pneumatics
Oil (typical)	850	20°C	Lubrication systems
Gasoline	750	20°C	Fuel systems
Steam (saturated)	0.598	100°C	Power generation
Natural gas	0.717	15°C, 1 atm	Gas distribution

Flow Rate Examples & Applications

🏠 HVAC Systems

Residential AC: 400-1200 CFM
Commercial HVAC: 2000-10000 CFM
Bathroom fan: 50-110 CFM
Range hood: 100-600 CFM
Central air handler: 1000-4000 CFM

🚿 Plumbing Systems

Kitchen faucet: 1.5-2.5 GPM
Shower head: 1.5-2.5 GPM
Toilet flush: 1.28-1.6 GPM
Garden hose: 5-10 GPM
Fire sprinkler: 15-30 GPM

🏭 Industrial Applications

Water treatment: 100-1000 m³/h
Chemical processes: 1-50 kg/s
Steam turbine: 100-500 t/h
Cooling tower: 1000-5000 GPM
Compressed air: 100-1000 CFM

🚗 Automotive

Fuel injector: 0.1-0.5 L/min
Water pump: 50-200 L/min
Oil pump: 20-80 L/min
Air intake: 200-800 CFM
Exhaust gas: 100-400 CFM

Practical Calculation Examples

Example 1: HVAC Design

Problem: Convert 2000 CFM to m³/s for international specifications.

2000 CFM × 4.719×10⁻⁴ = 0.944 m³/s

This is equivalent to about 3400 m³/h, suitable for a medium commercial space.

Example 2: Pump Selection

Problem: A pump delivers 500 L/min of water. What's the mass flow rate?

500 L/min = 8.33 L/s = 0.00833 m³/s

Mass flow = 0.00833 × 1000 = 8.33 kg/s

This corresponds to about 30 t/h of water flow.

Example 3: Gas Flow Conversion

Problem: Convert 100 CFM of air to kg/s.

100 CFM = 0.0472 m³/s

Mass flow = 0.0472 × 1.225 = 0.0578 kg/s

This equals about 208 kg/h of air flow at standard conditions.

Flow Rate Measurement Guide

🎯 Choosing the Right Unit

HVAC applications: Use CFM for air, GPM for water
International projects: Use m³/s or m³/h
Process industry: Use kg/s or kg/h for mass flow
Small systems: L/min or L/s are practical
Large systems: m³/h or t/h are appropriate

🌡️ Temperature & Pressure Effects

Gas flow rates change significantly with temperature
Always specify standard conditions for gas flows
Liquid flow rates are less affected by temperature
Pressure drops affect actual flow rates in systems
Use mass flow for processes sensitive to actual quantity

⚖️ Mass vs Volumetric Flow

Volumetric flow: Volume per unit time (m³/s, GPM)
Mass flow: Mass per unit time (kg/s, lb/s)
Mass flow remains constant despite pressure/temperature changes
Volumetric flow varies with fluid density
Chemical processes typically use mass flow rates

🔧 Measurement Methods

Orifice plates: Common for gas and liquid measurement
Turbine meters: High accuracy for clean liquids
Ultrasonic meters: Non-invasive measurement
Magnetic flowmeters: For conductive liquids
Pitot tubes: Simple velocity measurement in ducts

📏 Sizing Considerations

Pipe diameter affects velocity and pressure drop
Maintain reasonable velocities (2-6 m/s for liquids)
Consider pump or fan performance curves
Account for system losses and fittings
Size for future expansion when possible

⚠️ Common Mistakes

Confusing mass and volumetric flow rates
Ignoring temperature and pressure effects
Using wrong fluid density for conversions
Not accounting for system pressure losses
Oversizing equipment based on theoretical calculations

🌊 Flow Rate Unit Converter