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Flow Rate Calculator

Convert between flow rate units instantly
Enter a flow rate value and select the unit to convert to all other units.

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Flow Rate Conversion Guide

Understanding Flow Rate

Flow rate measures the volume of fluid passing through a given point per unit time. It's essential in HVAC, plumbing, chemical processing, and many engineering applications.

Common Metric Units:
  • L/min (LPM): Liters per minute - Pumps, water systems
  • L/s: Liters per second - Industrial flows
  • m³/h: Cubic meters per hour - Large systems, HVAC
  • m³/s: Cubic meters per second - Very large flows
  • ml/min: Milliliters per minute - Medical, lab equipment
Common Imperial Units:
  • GPM: Gallons per minute - Pumps, plumbing (US standard)
  • GPH: Gallons per hour - Fuel consumption, slow flows
  • CFM: Cubic feet per minute - Air flow, HVAC, ventilation
  • CFH: Cubic feet per hour - Gas flow, slow air systems
Quick Reference:
  • 1 GPM = 3.785 L/min ≈ 0.227 m³/h
  • 1 L/min ≈ 0.264 GPM ≈ 0.035 CFM
  • 1 CFM = 28.317 L/min ≈ 7.48 GPM
  • 1 m³/h = 16.67 L/min ≈ 4.4 GPM

Common Applications

  • HVAC: Air flow (CFM), water flow (GPM, L/min)
  • Plumbing: Water supply (GPM, L/min)
  • Pumps: Pump capacity (GPM, L/min, m³/h)
  • Medical: IV drips, dialysis (ml/min, ml/h)
  • Industrial: Chemical processing (m³/h, L/s)
Pro Tips
  • HVAC Tip
    CFM (air flow) and GPM (water flow) are different! 1 CFM ≠ 1 GPM.
  • Pump Selection
    Match pump flow rate to system requirements. Oversizing wastes energy.
  • Pressure Matters
    Flow rate varies with pressure. These conversions assume constant conditions.
Typical Flow Rates
  • Shower: 2-2.5 GPM (7.6-9.5 L/min)
  • Kitchen faucet: 1.5-2 GPM
  • Garden hose: 5-10 GPM
  • Fire hydrant: 500-1500 GPM

Frequently Asked Questions

Q: What's the difference between GPM and CFM?

A: GPM (Gallons Per Minute) measures liquid flow rate, typically water. CFM (Cubic Feet per Minute) measures gas/air flow rate. They measure different fluids, so 1 GPM ≠ 1 CFM. 1 CFM ≈ 7.48 GPM in volume, but they're used for different applications.

Q: How do I calculate flow rate from pipe size and velocity?

A: Flow Rate = Area × Velocity. For a circular pipe: Q = π × (diameter/2)² × velocity. For example, a 2-inch diameter pipe with water flowing at 5 ft/s: Q = 3.14 × (1 inch)² × 5 ft/s ≈ 0.87 CFM ≈ 6.5 GPM.

Q: What flow rate do I need for my application?

A: It depends on your application. Residential showers: 2-2.5 GPM. Kitchen faucets: 1.5-2 GPM. HVAC systems: varies by room size (typically 1 CFM per sq ft). Pool pumps: based on pool volume (turnover every 8-12 hours). Consult industry standards for specific applications.

Q: Does flow rate change with pressure?

A: Yes! Higher pressure generally increases flow rate (for a given pipe size). Flow rate is proportional to the square root of pressure difference. Doubling the pressure doesn't double the flow—it increases it by about 41% (√2). This calculator converts units, not pressure-dependent flows.

Q: What's a good flow rate for a water pump?

A: It depends on your needs. Sump pumps: 10-50 GPM. Well pumps: 5-15 GPM for residential. Pool pumps: sized to turn over pool volume in 8-12 hours. Irrigation: 5-20 GPM per zone. Always match pump capacity to your system requirements and avoid oversizing.

Q: How accurate are these conversions?

A: Our conversions use exact, internationally-defined conversion factors. Results are rounded to 8 decimal places. However, real-world flow rates can vary due to pressure, temperature, pipe friction, and fluid properties. Use these conversions for planning and specification, but measure actual flows for critical applications.

Disclaimer

Important Notice:

  • This calculator provides accurate unit conversions based on internationally-defined conversion factors.
  • Conversions are rounded to 8 decimal places for display. For scientific or precision applications, use specialized tools.
  • Actual flow rates depend on many factors: pressure, temperature, pipe size, friction, elevation, and fluid properties. This tool converts units only.
  • For HVAC systems, CFM requirements depend on room size, insulation, climate, and other factors. Consult HVAC professionals for system design.
  • For plumbing applications, flow rates are affected by water pressure, pipe diameter, and fixture requirements. Follow local plumbing codes.
  • Pump selection requires considering both flow rate AND pressure (head). Consult pump curves and manufacturer specifications.
  • Flow rate calculations assume steady-state conditions. Transient flows, turbulence, and compressibility effects are not considered.
  • For safety-critical applications (fire suppression, medical equipment, chemical processing), use certified flow meters and consult with qualified engineers.
  • Different fluids have different properties. Water flow rates cannot be directly applied to gases, oils, or other fluids without proper engineering analysis.
  • We are not responsible for any errors, equipment damage, system failures, or other consequences resulting from the use of this calculator.

Always consult with qualified professionals for system design and use calibrated flow meters for critical measurements.

Flow Rate Calculator

Convert between 10 common flow rate units instantly. Perfect for HVAC, plumbing, pumps, and engineering!

Supported Units
Metric:
  • ✓ L/min, L/s
  • ✓ m³/h, m³/s
  • ✓ ml/min, ml/s
Imperial:
  • ✓ GPM, GPH
  • ✓ CFM, CFH
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Flow Rate & Fluid Mechanics:

Did You Know?

Niagara Falls has a flow rate of about 750,000 gallons per second (2.8 million liters per second) during peak flow! That's enough to fill an Olympic swimming pool in less than 1 second!