Model flow through pipes with clear inputs today. Compare units, velocity, and capacity in seconds. Download summaries, verify assumptions, and share consistent calculations easily.
These examples illustrate typical combinations of diameter and velocity, with the resulting volumetric flow rate.
| Internal Diameter | Velocity | Flow Rate | Notes |
|---|---|---|---|
| 100 mm | 1.5 m/s | 0.0118 m³/s (42.4 m³/h) | Small transfer line |
| 150 mm | 2.0 m/s | 0.0353 m³/s (127.1 m³/h) | Moderate service velocity |
| 300 mm | 2.5 m/s | 0.1767 m³/s (636.1 m³/h) | High-capacity header |
Cross-sectional area: A = π·D²/4, where D is the internal diameter.
Volumetric flow rate: Q = A·V, where V is the average velocity.
Average velocity: V = Q/A, when flow rate is known.
Reynolds number: Re = ρ·V·D/μ, using density ρ and viscosity μ.
Head loss (optional): hf = f·(L/D)·(V²/(2g)).
Friction factor: 64/Re for laminar, and Swamee–Jain approximation for turbulent flow.
Volumetric flow rate links cross-sectional area and average velocity using Q = A×V. Area scales with D², so a 20% diameter increase raises capacity about 44% at constant velocity. For example, a 150 mm line at 2.0 m/s gives roughly 0.035 m³/s, aligning with the example table. These relations support quick feasibility checks before detailed hydraulic modeling. They also help screen tie-in sizes during debottlenecking studies and temporary bypass planning.
Velocity selection balances erosion, noise, pump power, and solids transport. Water service often tolerates moderate velocities, while slurries may need higher values to avoid settling. In gas lines, excessive velocity can increase pressure drop and vibration risk. Use the calculator’s velocity-to-flow mode to test multiple scenarios and keep results in consistent units for comparison. Document the chosen target range so future changes in throughput are evaluated consistently.
Reynolds number Re = ρVD/μ indicates whether flow is laminar, transitional, or turbulent. Small diameters, low velocities, or high viscosity push Re downward, increasing sensitivity to viscosity. Once turbulent, roughness becomes more influential and friction factor changes slowly with Re. Reporting Re and regime helps engineers validate whether selected correlations and assumptions remain appropriate. If Re falls in the transitional band, treat predictions cautiously and consider field data.
When losses are enabled, the calculator applies hf = f(L/D)(V²/2g) and converts head to pressure drop. The friction factor uses 64/Re for laminar flow and Swamee–Jain for turbulent conditions, requiring roughness ε. Longer runs, smaller diameters, and higher velocities increase losses sharply, guiding early pump sizing and system layout decisions. Pair this output with available static head and elevation profiles to estimate total differential head.
Exportable CSV and PDF summaries support reviews and traceability. Include diameter, mode, velocity, flow, and computed Re alongside head loss when applicable. Compare flows in m³/h, L/s, and gpm to match stakeholder conventions. If results drive procurement, add margins for fouling, aging, temperature-driven viscosity changes, and operational transients.
It reports volumetric flow rate in m³/s and also converts it into common engineering units such as m³/h, L/s, L/min, ft³/s, and US gpm.
Use the internal diameter that actually carries fluid. If you only know nominal size, confirm the pipe schedule or liner thickness to estimate true internal diameter.
Re indicates flow regime and influences friction factor selection. Low Re suggests laminar behavior, while high Re typically implies turbulent behavior where roughness effects become more significant.
It is a screening-level estimate using Darcy–Weisbach and a standard friction factor correlation. Minor losses, fittings, valves, and two-phase behavior are not included unless you account for them separately.
Choose a representative absolute roughness for the pipe material and condition. New pipe is smoother than aged pipe, so conservative projects often test a higher roughness to reflect fouling and wear.
Yes. Enter the correct density and dynamic viscosity for your fluid at operating temperature. If properties change with temperature, rerun cases at expected minimum and maximum temperatures.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.