Pipe Flow Rate Charts & Reference Tables
Pipe flow rate charts list the typical or maximum flow rate a pipe can carry for a given diameter, material, and design velocity, using Q = V × A. They let you size pipes at a glance — without manual calculation — by reading the flow rate straight from the table.
These pipe flow rate charts show the maximum recommended flow rates for standard pipe sizes based on design velocity limits. Use these tables for quick pipe sizing decisions, or use our interactive Pipe Flow Chart tool to generate custom tables at any velocity for Schedule 40 steel, Type L copper or Schedule 40 PVC.
All values are calculated using Q = V × A where A = π/4 × D², with actual inside diameters for Schedule 40 pipe.
Standard Pipe Sizes (Schedule 40)
| NPS | DN | Actual ID (in) | Actual ID (mm) | Area (in²) |
|---|---|---|---|---|
| 1/2" | DN15 | 0.622 | 15.80 | 0.304 |
| 3/4" | DN20 | 0.824 | 20.93 | 0.533 |
| 1" | DN25 | 1.049 | 26.64 | 0.864 |
| 1-1/4" | DN32 | 1.380 | 35.05 | 1.496 |
| 1-1/2" | DN40 | 1.610 | 40.89 | 2.036 |
| 2" | DN50 | 2.067 | 52.50 | 3.356 |
| 2-1/2" | DN65 | 2.469 | 62.71 | 4.788 |
| 3" | DN80 | 3.068 | 77.93 | 7.393 |
| 4" | DN100 | 4.026 | 102.26 | 12.730 |
| 6" | DN150 | 6.065 | 154.05 | 28.890 |
| 8" | DN200 | 7.981 | 202.72 | 50.027 |
| 10" | DN250 | 10.020 | 254.51 | 78.854 |
| 12" | DN300 | 11.938 | 303.23 | 111.932 |
Water Flow Rate Chart — Imperial (GPM)
Flow rates in US gallons per minute (GPM) for Schedule 40 pipe at various design velocities:
| Pipe Size | 3 ft/s | 5 ft/s | 8 ft/s | 10 ft/s |
|---|---|---|---|---|
| 1/2" | 2.8 | 4.7 | 7.6 | 9.5 |
| 3/4" | 5.0 | 8.3 | 13.3 | 16.6 |
| 1" | 8.1 | 13.5 | 21.6 | 26.9 |
| 1-1/4" | 14.0 | 23.3 | 37.3 | 46.6 |
| 1-1/2" | 19.0 | 31.7 | 50.8 | 63.5 |
| 2" | 31.4 | 52.3 | 83.7 | 104.6 |
| 2-1/2" | 44.8 | 74.6 | 119.4 | 149.2 |
| 3" | 69.1 | 115.2 | 184.3 | 230.4 |
| 4" | 119.0 | 198.4 | 317.4 | 396.8 |
| 6" | 270.1 | 450.2 | 720.4 | 900.5 |
| 8" | 467.8 | 779.6 | 1247.4 | 1559.3 |
| 10" | 737.3 | 1228.9 | 1966.2 | 2457.8 |
| 12" | 1046.6 | 1744.4 | 2791.0 | 3488.8 |
Values calculated as Q (GPM) = V (ft/s) × A (in²) × 3.1169 (conversion factor). Based on Schedule 40 actual inside diameters.
Water Flow Rate Chart — Metric (LPM)
Flow rates in liters per minute (LPM) for Schedule 40 pipe at various design velocities:
| Pipe Size | 1.0 m/s | 1.5 m/s | 2.5 m/s | 3.0 m/s |
|---|---|---|---|---|
| DN15 (1/2") | 11.8 | 17.6 | 29.4 | 35.3 |
| DN20 (3/4") | 20.6 | 31.0 | 51.6 | 61.9 |
| DN25 (1") | 33.5 | 50.2 | 83.6 | 100.4 |
| DN32 (1-1/4") | 57.9 | 86.8 | 144.7 | 173.7 |
| DN40 (1-1/2") | 78.8 | 118.2 | 197.0 | 236.4 |
| DN50 (2") | 129.9 | 194.8 | 324.7 | 389.7 |
| DN65 (2-1/2") | 185.3 | 278.0 | 463.3 | 556.0 |
| DN80 (3") | 286.2 | 429.3 | 715.4 | 858.5 |
| DN100 (4") | 492.8 | 739.2 | 1232.0 | 1478.4 |
| DN150 (6") | 1118.3 | 1677.5 | 2795.8 | 3355.0 |
| DN200 (8") | 1936.5 | 2904.8 | 4841.3 | 5809.6 |
| DN250 (10") | 3052.4 | 4578.6 | 7631.0 | 9157.3 |
| DN300 (12") | 4332.8 | 6499.2 | 10832.1 | 12998.5 |
Values calculated as Q (LPM) = V (m/s) × A (mm²) × 0.06 (conversion factor).
Recommended Design Velocities
Selecting the right design velocity is critical for balancing flow capacity, noise, and pipe wear:
| Application | Imperial | Metric | Notes |
|---|---|---|---|
| Domestic cold water | 4–8 ft/s | 1.2–2.4 m/s | Lower for quiet operation |
| Domestic hot water | 3–5 ft/s | 0.9–1.5 m/s | Lower to minimize erosion; 2–3 ft/s above 140°F |
| Commercial water | 4–10 ft/s | 1.2–3.0 m/s | Higher velocities acceptable |
| Fire protection | 10–15 ft/s | 3.0–4.6 m/s | NFPA limits apply |
| Cooling water | 5–10 ft/s | 1.5–3.0 m/s | Higher for heat transfer |
| Pump suction | 2–5 ft/s | 0.6–1.5 m/s | Low to prevent cavitation |
| Pump discharge | 5–12 ft/s | 1.5–3.7 m/s | Higher acceptable |
| Steam (low pressure) | 60–100 ft/s | 18–30 m/s | Gas velocities much higher |
| Compressed air | 20–30 ft/s | 6–9 m/s | Higher causes noise |
How to Use These Charts
- Determine your required flow rate based on the application (fixtures, equipment, or process demand).
- Select the appropriate design velocity from the table above based on your application type.
- Find the pipe size in the chart where the flow rate at your design velocity meets or exceeds your requirement.
- Verify pressure drop using our Pressure Drop Calculator to ensure losses are acceptable.
- Check noise and erosion — if velocity exceeds 8 ft/s (2.4 m/s) in residential systems, consider the next larger size.
Related Calculators
- Interactive Pipe Flow Chart Tool — Custom tables for steel, copper or PVC at any velocity
- Pipe Sizing Calculator — Find optimal pipe diameter for a given flow
- Velocity Calculator — Calculate fluid velocity from flow rate and pipe size
- Pressure Drop Calculator — Check friction losses for your selected pipe
- Flow Rate Calculator — Main pipe flow calculator
FAQ
Common questions about pipe flow rates and sizing.
Frequently Asked Questions
What is the maximum flow rate for a 2-inch pipe?
For a 2-inch Schedule 40 pipe (actual ID 2.067 inches), the flow rate depends on the design velocity. At the common design velocity of 5 ft/s, the maximum flow is approximately 52 GPM. At 8 ft/s, it increases to about 84 GPM. For fire protection at 10 ft/s, approximately 105 GPM.
What velocity should I use for pipe sizing?
For domestic cold water systems, use 4-8 ft/s (1.2-2.4 m/s). For hot water, use 3-5 ft/s to minimize erosion. Commercial and industrial systems can go higher, up to 10 ft/s. Fire protection systems are designed at 10-15 ft/s. Exceeding recommended velocities causes noise, vibration, and accelerated pipe wear.
What is the difference between nominal pipe size and actual inside diameter?
Nominal Pipe Size (NPS) is a standard label, not the actual measurement. For example, a 1-inch pipe (NPS 1) has an actual inside diameter of 1.049 inches for Schedule 40. The actual ID varies by wall thickness (schedule). Always use the actual inside diameter for flow calculations, not the nominal size.
Does pipe material affect the flow rate?
Yes, in two ways. First, the bore: at a given velocity the flow depends only on the inside diameter, but the same nominal size has a different bore in each material. 1/2-inch Type L copper is 0.545 inches inside against 0.622 inches for 1/2-inch Schedule 40 steel, so at 5 ft/s the copper carries about 3.6 GPM and the steel about 4.7 GPM. The tables on this page are Schedule 40 steel; the interactive Pipe Flow Chart also covers Type L copper and Schedule 40 PVC. Second, friction: smoother pipes like PVC (C=150) lose less pressure than old cast iron (C=100), so they can deliver more flow for the same available pressure.
How do I choose between two pipe sizes?
If your required flow falls between two sizes, always round up to the larger pipe. The larger pipe will have lower pressure drop, less noise, and more capacity for future expansion. The slightly higher material cost is typically offset by lower pump energy costs over the system lifetime. Use our Economic Pipe Diameter Calculator for a detailed cost comparison.
Free download
Get the printable pipe flow chart
Schedule 40 pipe sizes, water flow in GPM and LPM at four design velocities, and recommended velocities by application. One PDF, made to pin above the bench.
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