Select gas velocity, volume flow rate, or internal diameter, then enter the two required values with unit conversions for m³/s, ft³/s, m/s, and ft/s.
- All Physics Calculators
- All Velocity Calculators
- Stream Velocity Calculator
- Flow to Velocity Calculator
- Gas Piping Size Calculator
Natural Gas to Velocity Formula
The calculator uses the circular pipe flow relationship between volumetric flow rate, internal pipe diameter, and gas velocity. It converts all inputs to base units first: flow rate in m³/s, diameter in meters, and velocity in m/s.
- A = internal cross-sectional area of the pipe
- Q = volumetric flow rate of natural gas
- V = natural gas velocity
- D = internal diameter of the natural gas pipe
- pi = 3.14159265…
If you enter flow rate and pipe diameter, the calculator solves for velocity using V = Q / A. If you enter diameter and velocity, it solves for flow rate using Q = V × A. If you enter flow rate and velocity, it solves for the required internal diameter using D = √((4Q) / (πV)).
The result is based on volumetric flow through a round pipe. It does not adjust for pressure, temperature, gas compressibility, pipe roughness, fittings, or pressure drop.
Natural Gas Velocity and Unit Reference
The table below illustrates velocity magnitudes and unit conversions; these bands are not gas-piping design limits. Acceptable velocity requires the applicable code and an engineering assessment of pipe material, pressure drop, noise and operating conditions.
| Velocity Range | Approx. ft/s | General Interpretation |
|---|---|---|
| Less than 5 m/s | Less than 16.4 ft/s | Illustrative low-speed band; no compliance conclusion |
| 5 to 15 m/s | 16.4 to 49.2 ft/s | Illustrative speed band; no recommended design range |
| 15 to 30 m/s | 49.2 to 98.4 ft/s | Illustrative higher-speed band; assess pressure drop and noise separately |
| Greater than 30 m/s | Greater than 98.4 ft/s | Illustrative speed band; requires system-specific assessment |
These are the unit conversions used for the supported inputs and outputs.
| Quantity | Unit | Conversion to Base Unit |
|---|---|---|
| Flow rate | L/s | 1 L/s = 0.001 m³/s |
| Flow rate | ft³/s | 1 ft³/s = 0.028316846592 m³/s |
| Diameter | in | 1 in = 0.0254 m |
| Diameter | ft | 1 ft = 0.3048 m |
| Velocity | ft/s | 1 ft/s = 0.3048 m/s |
Example Calculations
Example 1: Calculate natural gas velocity
You have a volumetric flow rate of 0.10 m³/s through a pipe with an internal diameter of 0.10 m.
The natural gas velocity is about 12.73 m/s.
Example 2: Calculate required pipe diameter
You have a flow rate of 50 L/s and want a gas velocity of 8 m/s. First convert the flow rate:
The required internal diameter is about 0.0892 m, or 8.92 cm.
FAQs
Does this calculate standard or actual natural gas velocity?
It calculates velocity from the volumetric flow rate you enter. If your flow rate is actual m³/s at the pipe conditions, the velocity result is actual velocity. If your flow rate is a standard flow value corrected to standard temperature and pressure, you need to convert it to actual pipe conditions before using it for actual velocity.
Should I use nominal pipe size or internal diameter?
Use the internal diameter. Nominal pipe size is not always the same as the inside diameter, especially when wall thickness changes. A small difference in diameter can cause a noticeable difference in velocity because area depends on diameter squared.
Why does velocity increase when the pipe diameter gets smaller?
For the same volumetric flow rate, a smaller pipe has less cross-sectional area. Since velocity equals flow rate divided by area, reducing the area increases the velocity.
