Calculate saturated steam mass flow, pipe diameter, or velocity from pressure or specific volume, with metric and imperial units for preliminary pipe sizing.

Find mass flow from inside diameter, velocity and steam specific volume.

Preliminary continuity estimate. Verify pressure loss, condensate drainage, pipe schedule and applicable codes.

Dry saturated steam: 1–30 bar absolute. Gauge units assume 1.01325 bar atmosphere.

Related Calculators

Steam Flow Formula

The following continuity relation estimates steam mass flow from pipe inside diameter, bulk velocity and specific volume at the operating condition.

ṁ = (Au) / (vg); A = (π D²) / (4)

Variables:

  • ṁ is steam mass flow in kg/s; multiply by 3,600 for kg/h
  • A is pipe flow area in m², calculated from inside diameter D in meters
  • u is bulk steam velocity in m/s, and vg is specific volume in m³/kg at the actual steam condition

Calculate area from the pipe inside diameter, multiply by velocity, and divide by specific volume. The pressure route uses IAPWS-IF97 properties for dry saturated steam at 1–30 bar absolute. Gauge inputs assume 1.01325 bar atmospheric pressure. For known superheated conditions, enter the appropriate specific volume directly; pressure and temperature are not inferred from that value.

What is Steam Flow?

Steam flow refers to the rate at which steam passes through a given area, typically measured in pounds per hour (lb/h). It is an important parameter in the design and operation of boilers, steam turbines, and other equipment where steam is used as a working fluid. Accurate steam flow measurements are crucial for efficiency and safety in thermal power plants and industrial processes.

How to Calculate Steam Flow?

The following steps outline how to estimate the Steam Flow.

  1. First, obtain specific volume vg in m³/kg at the operating condition, either from the dry-saturated pressure route or from a suitable property source.
  2. Next, determine the pipe inside diameter D and convert it to meters.
  3. Next, calculate area A = πD²/4 in m² and determine steam velocity u in m/s.
  4. Next, apply the continuity relation ṁ = Au/vg.
  5. Finally, calculate mass flow in kg/s and convert to the desired mass-flow unit. Preliminary sizing also requires pressure-drop, steam-condition, condensate, pipe-schedule and code checks; a commonly cited 25–40 m/s distribution range is conditional guidance, not a safety or design acceptance test.
  6. After inserting the variables 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.

Specific volume vg = 0.200 m³/kg (a supplied operating-condition property).

Pipe inside diameter D = 100 mm = 0.100 m, so A = π(0.100)²/4 ≈ 0.007853981634 m².

Velocity u = 30 m/s. Then ṁ = A × 30 / 0.200 ≈ 1.178097245 kg/s, or 4,241.15008 kg/h.