Calculator Inputs
Use the responsive form below. It shows three columns on large screens, two on medium screens, and one on mobile.
Formula Used
1) Beta ratio
β = d / D
2) Bore area
A = πd2 / 4
3) Volumetric flow rate
Q = Cd × Y × A × √[(2ΔP / ρ) / (1 - β4)]
4) Mass flow rate
ṁ = ρ × Q
5) Velocity
v = Q / Area
How to Use This Calculator
- Choose liquid or gas mode.
- Enter differential pressure and its unit.
- Provide fluid density, bore diameter, and pipe diameter.
- Set the discharge coefficient for your meter design.
- For gases, choose automatic or manual expansibility handling.
- Enter upstream absolute pressure and heat ratio when gas mode is used.
- Enter viscosity to estimate Reynolds number.
- Select output units for flow, mass flow, and velocity.
- Press Calculate DP Flow to show results above the form.
- Use the CSV or PDF buttons to export the latest calculation.
Example Data Table
| Case | Fluid | Pipe Diameter | Bore Diameter | DP | Density | Cd | Approx. Flow |
|---|---|---|---|---|---|---|---|
| 1 | Water | 100 mm | 50 mm | 5 kPa | 998 kg/m³ | 0.61 | 14.11 m³/h |
| 2 | Air | 150 mm | 75 mm | 2.5 kPa | 1.20 kg/m³ | 0.62 | 1,043.00 m³/h |
| 3 | Oil | 80 mm | 35 mm | 12 psi | 850 kg/m³ | 0.60 | 36.42 m³/h |
These examples are illustrative. Actual installed performance depends on meter type, piping conditions, calibration, and reference standard.
Frequently Asked Questions
1) What does a DP flow meter calculator estimate?
It estimates flow rate from a measured pressure drop across a restriction. The tool also reports mass flow, pipe velocity, bore velocity, beta ratio, and Reynolds number.
2) Why does flow increase with the square root of differential pressure?
Restriction flow devices follow an energy balance where pressure drop converts into velocity. Because velocity depends on the square root of pressure difference, flow does too.
3) When should I use expansibility factor Y?
Use it for gases and vapors when density changes across the meter are meaningful. Liquids are usually treated as incompressible, so Y is typically taken as 1.0.
4) What is beta ratio in a DP meter?
Beta ratio is bore diameter divided by pipe diameter. It strongly affects sensitivity, pressure drop, discharge behavior, and the usable measurement range.
5) Why is Reynolds number shown?
Reynolds number helps you judge the flow regime and whether your discharge coefficient is suitable. Low Reynolds flow may need more careful calibration or correction.
6) Can this calculator be used for liquids and gases?
Yes. Choose liquid for incompressible service and gas for compressible service. Gas mode also allows automatic or manual expansibility handling.
7) Does this replace a certified meter calculation sheet?
No. It is a practical engineering calculator for sizing, checking, and quick comparisons. Final custody or compliance work should follow the applicable reference standard and calibration data.
8) Why might field flow differ from this result?
Real systems include installation effects, non-ideal upstream piping, fluid property drift, transmitter error, edge wear, and actual discharge coefficient differences. These factors can shift measured flow.