Flow Converter
Convert volumetric flow rate between liters/second, gallons/minute, cubic meters/hour, CFM, and more. Used in HVAC, plumbing, hydraulics, and chemical processing. See also our Mass Flow Rate Converter and Molar Flow Rate Converter.
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Popular Flow Converters:
What is a Flow Converter?
A flow rate converter is a tool that converts between units of volumetric flow such as liters per second, gallons per minute (GPM), cubic meters per hour, and cubic feet per minute (CFM). It is essential for HVAC design, plumbing, hydraulic engineering, and water treatment.
History of Flow Measurement
Flow measurement dates back to ancient civilizations that built aqueducts and irrigation systems. Modern flow measurement began with the Venturi meter in the 18th century. The cubic meter per second is the SI unit, while GPM dominates American plumbing and CFM is standard for HVAC airflow.
About This Flow Converter
This flow converter supports 15 units including liter/second, liter/minute, cubic meter/second, cubic meter/hour, cubic foot/minute (CFM), cubic foot/second, gallon (US)/minute (GPM), gallon/hour, and milliliter/second. It covers both SI and US customary flow units.
Understanding Fluid Flow Rate Measurement
Flow rate (volumetric flow) measures the volume of fluid passing through a cross-section per unit time. It is fundamental to hydraulic engineering, HVAC design, water treatment, chemical processing, and plumbing. Common units include liters per second (L/s), cubic meters per hour (m³/h), US gallons per minute (GPM), and cubic feet per minute (CFM). The wide variety of units reflects different industries and national conventions.
Flow rate conversion is essential because specifications come from multiple sources using different unit systems. A pump manufacturer may rate capacity in GPM, while a process engineer designs in m³/h, and regulatory discharge permits use L/s. HVAC engineers in the US size ductwork in CFM, while international standards use m³/h or L/s. Converting accurately between these units ensures equipment is properly sized — an undersized pump means insufficient flow, while oversized means wasted energy and capital.
How to Convert Between Flow Rate Units
Flow rate conversion combines volume unit conversion with time unit conversion:
- Identify the volume component (liters, m³, gallons, ft³) and time component (s, min, h) of both source and target units.
- Convert the volume: 1 m³ = 1000 L; 1 US gallon = 3.78541 L; 1 ft³ = 28.3168 L.
- Convert the time: 1 h = 60 min = 3600 s.
- Combine: for example, GPM to L/s = 3.78541 L/gal ÷ 60 s/min = 0.063090 L/s per GPM.
- Verify the conversion makes dimensional sense and the magnitude is reasonable.
Key Flow Rate Conversion Formulas
Essential flow rate relationships for hydraulic and HVAC engineering:
- 1 m³/h = 0.27778 L/s = 4.40287 GPM
- 1 L/s = 3.6 m³/h = 15.8503 GPM
- 1 GPM (US) = 0.063090 L/s = 0.227125 m³/h
- 1 CFM = 0.471947 L/s = 1.69901 m³/h
- 1 m³/s = 1000 L/s = 35.3147 ft³/s
- 1 L/min = 0.264172 GPM = 0.016667 L/s
- 1 GPM = 0.002228 ft³/s (CFS)
Worked Examples — Flow Rate Conversions
Example 1: A pump is rated at 500 GPM. What is the flow rate in m³/h?
Solution:
Conversion: 1 GPM = 0.227125 m³/h.
Multiply: 500 × 0.227125 = 113.56 m³/h.
Answer: 500 GPM = 113.6 m³/h — a medium-sized industrial pump.
Example 2: An HVAC system requires 2000 CFM of air. Convert to m³/h.
Solution:
Conversion: 1 CFM = 1.69901 m³/h.
Multiply: 2000 × 1.69901 = 3398 m³/h.
Answer: 2000 CFM = 3398 m³/h of airflow.
Example 3: A water treatment plant processes 450 L/s. Express in GPM and m³/h.
Solution:
GPM: 450 × 15.8503 = 7133 GPM.
m³/h: 450 × 3.6 = 1620 m³/h.
Answer: 450 L/s = 7133 GPM = 1620 m³/h — a large municipal plant.
Example 4: A fire hydrant delivers 1500 GPM. What is this in L/s?
Solution:
Conversion: 1 GPM = 0.063090 L/s.
Multiply: 1500 × 0.063090 = 94.64 L/s.
Answer: 1500 GPM = 94.6 L/s — typical flow for a major fire hydrant.
Flow Rate Conversion Quick Reference
Common flow rate conversions for hydraulic, HVAC, and process engineering:
| From | To |
|---|---|
| 1 L/s | 15.8503 GPM |
| 1 GPM | 0.06309 L/s |
| 1 m³/h | 4.40287 GPM |
| 1 CFM | 1.699 m³/h |
| 1 L/s | 3.6 m³/h |
| 1 m³/s | 1000 L/s |
| 1 GPM | 3.78541 L/min |
| 1 ft³/s (CFS) | 448.83 GPM |
| 1 L/min | 0.264172 GPM |
| 1 m³/h | 0.27778 L/s |
| 1 imperial GPM | 0.07577 L/s |
| 1 barrel/day | 0.00184 L/s |
Understanding Flow Rate Measurement Systems
The SI-derived unit of volumetric flow rate is m³/s, but this is impractically large for most applications (1 m³/s = 15,850 GPM). Instead, L/s and m³/h dominate in metric-country engineering: L/s for water supply and fire protection, m³/h for process plants and HVAC. The metric system's advantage is transparent conversion between flow and velocity: flow (m³/s) = velocity (m/s) × area (m²).
The US customary system uses gallons per minute (GPM) for liquid flow — universally in plumbing, fire protection, and pump specifications. For gas and air flow, cubic feet per minute (CFM) is standard in HVAC, compressed air, and ventilation. The oil industry uses barrels per day (1 barrel = 42 US gallons = 159 liters). The UK uses imperial gallons (1 imperial gallon = 4.546 L, 20% larger than US gallon), so "GPM" means different actual volumes depending on which country's gallon is used — always clarify.
Real-World Applications of Flow Rate Conversion
HVAC Engineering
Ventilation requirements in CFM (US) or m³/h (international) must match for equipment selection. A 10,000 CFM air handling unit = 16,990 m³/h. International projects require conversion between standards like ASHRAE (CFM) and EN (m³/h).
Water & Wastewater
Municipal water systems size pipes and pumps in GPM (US) or L/s (metric). Discharge permits may specify limits in million gallons per day (MGD) or m³/day. Converting correctly ensures regulatory compliance.
Fire Protection
Sprinkler systems are designed to deliver specific GPM per square foot (US) or L/min/m² (metric). Fire pump ratings, hydrant flow tests, and water supply calculations all require accurate flow conversion.
Process Engineering
Chemical reactors, heat exchangers, and distillation columns are designed using m³/h in most of the world, but US plants use GPM. Equipment purchased from international suppliers must have flow ratings converted correctly.
Oil & Gas Production
Well production rates in barrels per day, pipeline flow in m³/h, and refinery throughput in GPM all coexist. A single project may involve all three, requiring constant conversion for material balance calculations.
Common Pitfalls in Flow Rate Conversion
The most dangerous error is confusing US gallons with imperial gallons — a 20% difference that compounds into major sizing errors. "500 GPM" means 500 × 3.785 = 1893 L/min in the US, but 500 × 4.546 = 2273 L/min in the UK. Always clarify the gallon definition. Another critical pitfall is confusing CFM with CMM (cubic meters per minute) — they differ by a factor of 35.31, not the 28.32 you might expect from ft³-to-L conversion (because m³ ≠ L in magnitude). Also, be careful about "standard" vs "actual" conditions for gas flow: SCFM (standard cubic feet per minute) refers to a specific temperature and pressure, while ACFM is at actual operating conditions. These can differ by 50% or more and are NOT simple unit conversions — they require gas law corrections.
Key Takeaways
- 1 GPM = 0.0631 L/s is the key US-to-metric liquid flow conversion.
- 1 CFM = 1.699 m³/h is essential for HVAC air flow conversion.
- Always specify US or imperial gallons — they differ by 20% (3.785 L vs 4.546 L).
- Flow rate = velocity × cross-sectional area: this relationship aids unit verification.
- For water at standard conditions: 1 L/s flow rate = 1 kg/s mass flow rate (density ≈ 1 kg/L).
- Industrial flows typically use m³/h; research and standards often use L/s; US practice uses GPM or CFM.
Metric Conversion Factor Tables for Flow Converter
| Units to convert | Multiply By The Number | Convert as Unit |
|---|---|---|
| Liter/second (L/s) | 60 | Liter/minute (L/min) |
| Liter/minute (L/min) | 0.0166667 | Liter/second (L/s) |
| Liter/second (L/s) | 15.850323 | Gallon (US)/minute (gpm) |
| Gallon (US)/minute (gpm) | 0.0630902 | Liter/second (L/s) |
| Cubic meter/second (m³/s) | 1000 | Liter/second (L/s) |
| Cubic foot/minute (cfm) | 0.471947 | Liter/second (L/s) |
| Cubic meter/hour (m³/h) | 0.277778 | Liter/second (L/s) |
Flowconverters & it's abbreviations
| Unit | Abbreviation | Unit | Abbreviation | Unit | Abbreviation |
|---|---|---|---|---|---|
| cubic meter/second | m³/s | cubic meter/minute | m³/min | cubic meter/hour | m³/h |
| liter/second | L/s | liter/minute | L/min | liter/hour | L/h |
| cubic foot/second | ft³/s | cubic foot/minute | ft³/min | cubic foot/hour | ft³/h |
| gallon (US)/second | gal/s | gallon (US)/minute | gpm | gallon (US)/hour | gal/h |
| gallon (US)/day | gal/day | cubic centimeter/second | cm³/s | milliliter/second | mL/s |
Frequently Asked Questions
How do I convert liters per second to GPM?
Multiply the L/s value by 15.8503 to get gallons per minute. For example, 2 L/s × 15.8503 = 31.7 GPM.
What is CFM and what is it used for?
CFM stands for cubic feet per minute. It is the standard unit for measuring airflow in HVAC systems, ventilation fans, and air compressors in the United States.
How do I convert cubic meters per hour to liters per second?
Divide the m³/h value by 3.6 to get L/s. For example, 36 m³/h ÷ 3.6 = 10 L/s.
What is the difference between flow rate and velocity?
Flow rate is the volume of fluid passing a point per unit time (e.g., L/s). Velocity is the speed of the fluid (e.g., m/s). Flow rate = velocity × cross-sectional area of the pipe.
How do I convert GPM to cubic meters per hour?
Multiply the GPM value by 0.2271 to get m³/h. For example, 100 GPM × 0.2271 = 22.71 m³/h.
Complete list of Flow conversion units and its conversion.
- 1 liter/second = 60 liter/minute
L/s to L/min → - 1 liter/minute = 0.0166667 liter/second
L/min to L/s → - 1 liter/second = 15.850323 gallon (US)/minute
L/s to gpm →
- 1 cubic meter/hour = 4.40287 gallon (US)/minute
m³/h to gpm → - 1 cubic foot/second = 448.831 gallon (US)/minute
cfs to gpm →
- 1 gallon (US)/minute = 0.0630902 liter/second
gpm to L/s → - 1 cubic meter/second = 1000 liter/second
m³/s to L/s → - 1 cubic foot/minute = 0.471947 liter/second
cfm to L/s →