Calculate Flow Velocity from Flow Rate

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Flow Velocity Calculator

This calculator helps you determine the velocity of a fluid flowing through a pipe or channel based on the flow rate and the cross-sectional area of the flow. Understanding flow velocity is crucial in many engineering and scientific applications, from designing plumbing systems to analyzing fluid dynamics in natural waterways.

m³/s L/s GPM (US) m³/min

m² cm² ft² in²



How Flow Velocity is Calculated

The fundamental principle behind calculating flow velocity is the continuity equation, which states that for an incompressible fluid, the mass flow rate must be constant throughout a system. In simpler terms, the volume of fluid passing a point per unit time (flow rate) is equal to the cross-sectional area through which it flows multiplied by the average velocity of the fluid.

The formula is:

Velocity (v) = Flow Rate (Q) / Cross-Sectional Area (A)

To use this calculator:

  1. Enter the Flow Rate of the fluid.
  2. Select the appropriate unit for your Flow Rate (e.g., cubic meters per second, liters per second, gallons per minute).
  3. Enter the Cross-Sectional Area of the pipe or channel the fluid is flowing through.
  4. Select the appropriate unit for your Cross-Sectional Area (e.g., square meters, square centimeters, square feet).
  5. Click "Calculate Velocity".

The calculator will output the flow velocity in meters per second (m/s).

Units Conversion:

For your convenience, the calculator handles common unit conversions internally:

  • Flow Rate:
    • 1 m³/s = 1000 L/s
    • 1 m³/s ≈ 15850.32 GPM (US)
    • 1 m³/s = 60 m³/min
  • Area:
    • 1 m² = 10,000 cm²
    • 1 m² ≈ 10.764 ft²
    • 1 m² ≈ 1550 in²
function calculateFlowVelocity() { var flowRateInput = parseFloat(document.getElementById("flowRate").value); var flowRateUnit = document.getElementById("flowRateUnit").value; var crossSectionalAreaInput = parseFloat(document.getElementById("crossSectionalArea").value); var areaUnit = document.getElementById("areaUnit").value; var resultDiv = document.getElementById("result"); if (isNaN(flowRateInput) || isNaN(crossSectionalAreaInput) || flowRateInput < 0 || crossSectionalAreaInput <= 0) { resultDiv.innerHTML = "Please enter valid positive numbers for flow rate and a positive number for cross-sectional area."; return; } var flowRate_m3_per_sec; switch (flowRateUnit) { case "m3_per_sec": flowRate_m3_per_sec = flowRateInput; break; case "l_per_sec": flowRate_m3_per_sec = flowRateInput / 1000; break; case "gpm": flowRate_m3_per_sec = flowRateInput / 15850.32; break; case "m3_per_min": flowRate_m3_per_sec = flowRateInput / 60; break; } var crossSectionalArea_m2; switch (areaUnit) { case "m2": crossSectionalArea_m2 = crossSectionalAreaInput; break; case "cm2": crossSectionalArea_m2 = crossSectionalAreaInput / 10000; break; case "sq_ft": crossSectionalArea_m2 = crossSectionalAreaInput / 10.764; break; case "sq_in": crossSectionalArea_m2 = crossSectionalAreaInput / 1550; break; } var velocity_m_per_sec = flowRate_m3_per_sec / crossSectionalArea_m2; resultDiv.innerHTML = "Calculated Flow Velocity: " + velocity_m_per_sec.toFixed(3) + " m/s"; }

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