Gas Compressor Power calculator
What it costs to put the pressure back that the line just took.
Oil & Gas · Professional Microtool
Pipeline Pressure Drop Calculator
Outlet pressure · Velocity · Erosional limit
Outlet pressure along a gas pipeline from the isothermal flow equation, with the friction factor taken from the flow itself and the acceleration term solved by iteration rather than dropped.
Start from an example: 100 MMSCFD through 100 km of 590 mm line at 70 bar a →
Full output
- —Pressure drop
- —Drop as a share of inlet
- —Drop per kilometre
- —Velocity at outlet
- —Erosional limit at outlet
- —Velocity at inlet
- —Mass flow
- —Reynolds number
- —Friction factor
Outlet pressure against throughput
Pressure enters the equation squared, so the curve falls away faster and faster: doubling throughput costs roughly four times the drop, which is why a line that looks comfortable today runs out of capacity abruptly rather than gradually.
Keep it
Both carry the figures you entered, in the part of the address that is never sent to a server. Share only where that is appropriate. To keep a copy for a project file, print the page — it lays itself out as a document.
Need a production-ready pipeline model?
We can extend this calculation to real elevation, compressor stations, operating telemetry and your actual pipeline data.
Calculation basis 5 steps · view the method →
Mass flow = standard flow × density at 0 °C and 101.325 kPa—Reynolds number = mass flux × diameter ÷ viscosity—Friction factor from Swamee-Jain on that Reynolds number and the relative roughness—P₁² − P₂² = G²·Z·R·T·(f·L/D + 2·ln(P₁/P₂)), solved for P₂ by iteration—Velocity at the outlet, where the gas is least dense and therefore fastest—
Assumptions & limitations Screening estimate for hydraulic checks and capacity questions · 8 assumptions →
This is a screening calculation for steady, isothermal, single-phase gas in a horizontal line of constant bore. It excludes elevation change, liquid holdup and two-phase flow, heat transfer with the ground, fittings and valves, compressor station effects, transient and packing behaviour, and any real-gas treatment beyond a single Z. Design, rating and regulatory work require a proper hydraulic model and the applicable pipeline code — this figure is for orientation only.
- Steady, isothermal, single-phase gas flow in a horizontal line of constant internal diameter.
- Elevation change is ignored, which matters on hilly terrain and for dense gas.
- Liquid holdup and two-phase behaviour are not modelled; any condensate changes the answer substantially.
- Gas properties — Z, molecular weight and viscosity — are taken as constant along the segment.
- Fittings, valves, bends, station piping and metering losses are excluded.
- The erosional velocity uses API RP 14E with C = 100 in field units, a rule of thumb rather than a limit derived for your service.
- Transient and line-pack behaviour is out of scope: this is a steady-state answer.
- Where the flow cannot be carried from the given inlet pressure, the tool reports that there is no steady-state solution rather than an outlet of zero — and near sonic conditions this model stops being applicable well before that point.
Worked examples
- 100 MMSCFD through 100 km of 590 mm line at 70 bar a
Open with these figures → - Doubling the throughput to 200 MMSCFD
Open with these figures → - The same duty through a 400 mm line instead
Open with these figures →
About this tool
Pipeline hydraulics is where a screening number is most useful and most often taken too far. This tool runs the isothermal flow equation properly — friction from the actual Reynolds number, the expansion term solved rather than assumed away — and reports the velocity against the erosional limit, which is the check that decides whether a line is workable at all. Written for pipeline, facilities and process engineers.
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