Calculate liquid flow in litres per second from kPa pressure drop, or solve pressure drop or orifice diameter using density and discharge coefficient.

Use the differential pressure across the opening.

Simple circular-orifice liquid estimate. Pressure alone does not determine flow. Excludes pipe beta ratio, approach velocity, viscosity, cavitation and gas flow; use calibrated data for engineering design.

Presets are approximate; density depends on composition and temperature.

Discharge coefficient (default 0.62)

0.62 is an estimate, not a universal calibration. Use a tested coefficient when available.

kPa โ†” L/s (Orifice) Conversion Table (d = 10 mm, Cd = 0.62, ฯ = 1000 kg/mยณ)
kPa to L/s L/s to kPa
1 kPa = 0.0689 L/s0.05 L/s = 0.5272 kPa
2 kPa = 0.0974 L/s0.10 L/s = 2.1087 kPa
3 kPa = 0.1193 L/s0.15 L/s = 4.7445 kPa
5 kPa = 0.1540 L/s0.20 L/s = 8.4346 kPa
7 kPa = 0.1822 L/s0.25 L/s = 13.1791 kPa
10 kPa = 0.2178 L/s0.30 L/s = 18.9780 kPa
15 kPa = 0.2667 L/s0.35 L/s = 25.8311 kPa
20 kPa = 0.3080 L/s0.40 L/s = 33.7386 kPa
25 kPa = 0.3443 L/s0.50 L/s = 52.7165 kPa
30 kPa = 0.3772 L/s0.60 L/s = 75.9118 kPa
40 kPa = 0.4355 L/s0.75 L/s = 118.6122 kPa
50 kPa = 0.4869 L/s0.80 L/s = 134.9543 kPa
60 kPa = 0.5334 L/s0.90 L/s = 170.8016 kPa
75 kPa = 0.5964 L/s1.00 L/s = 210.8661 kPa
100 kPa = 0.6886 L/s1.25 L/s = 329.4784 kPa
125 kPa = 0.7699 L/s1.50 L/s = 474.4488 kPa
150 kPa = 0.8434 L/s1.75 L/s = 645.7776 kPa
200 kPa = 0.9739 L/s2.00 L/s = 843.4646 kPa
250 kPa = 1.0888 L/s2.50 L/s = 1317.9134 kPa
300 kPa = 1.1928 L/s3.00 L/s = 1897.7953 kPa
Formula: Q = CdยทAยทโˆš(2ฮ”P/ฯ). This table assumes d = 10 mm, Cd = 0.62, ฯ = 1000 kg/mยณ.

kPa To Litres Per Second Formula

The following circular-orifice model estimates steady incompressible liquid flow from differential pressure, opening diameter, liquid density and a discharge coefficient. Pressure alone cannot determine flow.

Q = Cd A โˆš(2ฮ” P / ฯ), A = ฯ€ dยฒ / 4

Variables:

  • Q is flow in mยณ/s in the equation; multiply by 1,000 for litres per second
  • ฮ”P is the pressure difference in Pa; multiply entered kPa by 1,000
  • Cd is the dimensionless discharge coefficient; A is circular opening area in mยฒ, d is diameter in m, and ฯ is liquid density in kg/mยณ

Calculate the circular area, then multiply it by Cd and โˆš(2ฮ”P/ฯ). This simple-orifice estimate excludes pipe beta ratio, approach velocity, viscosity, cavitation and compressible gases. Use calibrated data for engineering design.

How to Calculate Flow Rate?

The following steps outline how to calculate the flow rate.

  1. First, determine the pressure drop ฮ”P across the opening in kilopascals.
  2. Next, measure the circular orifice diameter d in millimetres.
  3. Next, choose a liquid density and an appropriate discharge coefficient. Preset densities and Cd = 0.62 are approximate assumptions.
  4. Finally, convert pressure to Pa and diameter to m, then calculate Q = Cd ร— (ฯ€dยฒ/4) ร— โˆš(2ฮ”P/ฯ). Multiply mยณ/s by 1,000 for L/s.
  5. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Pressure drop ฮ”P = 100 kPa

Orifice diameter d = 10 mm

For ฯ = 1,000 kg/mยณ and Cd = 0.62, Q โ‰ˆ 0.6886 L/s. This is an orifice-flow estimate, not a direct pressure-to-flow unit conversion.