Pipe Velocity Calculator
Calculate flow velocity in pipes and see erosion/sedimentation risk warnings. Supports liquids, gases, and steam. Includes industry-standard velocity limits by service type.
Calculate Pipe Velocity
Velocity Formula: v = Q / A
v = Velocity | Q = Volumetric flow rate | A = Pipe cross-sectional area
US Units: v (ft/s) = Q (GPM) × 0.408 / ID² (in²)
Metric: v (m/s) = Q (m³/hr) / (3600 × π × ID² (m²) / 4)
v = Velocity | Q = Volumetric flow rate | A = Pipe cross-sectional area
US Units: v (ft/s) = Q (GPM) × 0.408 / ID² (in²)
Metric: v (m/s) = Q (m³/hr) / (3600 × π × ID² (m²) / 4)
US GPM
Nominal pipe size
For risk assessment
Typical velocity ranges: Water 5-10 ft/s | Steam 30-60 ft/s | Natural Gas 20-60 ft/s | Air 20-50 ft/s | Slurry 3-8 ft/s
Velocity Result
Pipe Internal Diameter–
Flow Area–
Velocity–
Velocity Status–
0LowOptimalHighMax
Erosion Risk–
Sedimentation Risk–
Recommendation–
Recommended Velocity Limits by Service
| Service | Min Velocity | Recommended | Max Velocity | Notes |
|---|---|---|---|---|
| Water (Suction) | 2 ft/s (0.6 m/s) | 3-5 ft/s (0.9-1.5 m/s) | 8 ft/s (2.4 m/s) | Avoid cavitation |
| Water (Discharge) | 3 ft/s (0.9 m/s) | 5-10 ft/s (1.5-3 m/s) | 15 ft/s (4.5 m/s) | General water distribution |
| Steam (Saturated) | 20 ft/s (6 m/s) | 30-50 ft/s (9-15 m/s) | 80 ft/s (24 m/s) | Higher in large pipes |
| Steam (Superheated) | 30 ft/s (9 m/s) | 50-80 ft/s (15-24 m/s) | 120 ft/s (36 m/s) | Check erosion allowance |
| Natural Gas | 10 ft/s (3 m/s) | 20-60 ft/s (6-18 m/s) | 100 ft/s (30 m/s) | API 14E limits apply |
| Compressed Air | 10 ft/s (3 m/s) | 20-50 ft/s (6-15 m/s) | 80 ft/s (24 m/s) | Watch for pressure drop |
| Slurry (Abrasive) | 3 ft/s (0.9 m/s) | 4-8 ft/s (1.2-2.4 m/s) | 10-12 ft/s (3-3.6 m/s) | Minimize settling |
| Oil (Light) | 2 ft/s (0.6 m/s) | 5-15 ft/s (1.5-4.5 m/s) | 20 ft/s (6 m/s) | Check viscosity effects |
| Oil (Heavy) | 1 ft/s (0.3 m/s) | 2-5 ft/s (0.6-1.5 m/s) | 8 ft/s (2.4 m/s) | Higher viscosity = lower vel |
API 14E Erosional Velocity: For gas/liquid mixtures: Ve = C / sqrt(ρ) where C = 100-150 (clean), 75-100 (with solids), ρ = mixture density (lb/ft³). Exceeding Ve causes rapid erosion in carbon steel.
Find Required Pipe Size for Target Velocity
Enter flow rate and target velocity to find the minimum pipe size needed:
US GPM
ft/s
Recommended Pipe Size
Minimum ID Required–
Recommended NPS–
Actual Velocity–
Next Size Up (if needed)–
Pipe Velocity Engineering Guide
Why Velocity Matters
- Erosion: High velocity causes particle impact erosion on pipe walls and valve internals. In carbon steel, velocities >15-20 ft/s with abrasive particles cause significant wear.
- Cavitation: Low pressure zones at fittings can cause cavitation even at moderate velocities if local pressure drops below vapor pressure.
- Noise: High velocity (especially >50 ft/s) causes aerodynamic noise and vibration.
- Water Hammer: Rapid velocity changes in liquid systems cause pressure surges. Keep velocities moderate if frequent valve operations occur.
- Sedimentation: Low velocity allows suspended solids to settle out, causing blockages and corrosion under deposits.
- Bacterial Growth: Stagnant water (velocities <1 ft/s) allows Legionella and other bacteria to proliferate.
Design Best Practices
- Size pipes for velocity in the "recommended" range, not just pressure drop
- For variable flow systems, design for velocity at minimum flow condition (avoid sedimentation)
- In slurry service, always verify particles remain in suspension at minimum flow
- For steam, velocity increases with pipe size — larger pipes allow higher velocities
- Use eccentric reducers (not concentric) at pump discharges to avoid air pockets
Need Help with Pipe Sizing?
Our engineering team can help size piping systems and select valves optimized for your flow conditions.