Flow Rate Calculator
Flow Rate Calculator (Q = V × A)
About the Flow Rate Calculator
The Flow Rate Calculator is a free, accurate, and easy-to-use online tool that instantly computes volumetric flow rate (Q) using the fundamental continuity equation Q = V × A. Whether you are a mechanical engineer, plumber, irrigation designer, or student, this calculator helps you determine how much fluid passes through a pipe or channel per unit time.
What is Flow Rate?
Flow Rate (often denoted as Q) is the volume of fluid that passes through a given surface per unit time. It is one of the most important parameters in fluid mechanics and hydraulic engineering.
Why Use This Flow Rate Calculator?
Accurate flow rate calculation is critical in countless real-world applications. Incorrect values can lead to undersized pumps, inefficient systems, or even complete project failure. This Flow Rate Calculator eliminates manual errors and delivers results in multiple units (CFS, GPM, LPS, m³/h) with just one click.
When and Why Should You Use This Calculator?
- Sizing water supply and wastewater pipes
- Designing irrigation and sprinkler systems
- Selecting the correct pump or fan
- HVAC duct sizing and airflow calculations
- Fire protection system hydraulic modeling
- Open channel and stormwater drainage design
- Industrial process piping
How to Use – Step by Step
- Enter fluid velocity in feet per second (ft/s)
- Input pipe diameter (inches) or rectangular dimensions
- Select circular or rectangular shape
- Click “Calculate Flow Rate”
- Get instant results in 4 different units
Common Velocity Guidelines
| Application | Recommended Velocity |
|---|---|
| Water supply lines | 3–8 ft/s |
| Pump suction lines | 2–4 ft/s |
| HVAC chilled water | 4–10 ft/s |
| Fire hydrant lines | Up to 15 ft/s |
| Drainage pipes | Minimum 2 ft/s (self-cleaning) |
Flow Rate Units Conversion Table
- 1 cfs = 448.8 GPM
- 1 GPM = 0.06309 liters/second
- 1 m³/hour = 4.403 GPM
- 1 liter/second = 15.85 GPM
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Advantages of This Calculator
- Supports both circular pipes and rectangular ducts
- Shows results in US and metric units simultaneously
- No software installation required
- Mobile-friendly and fast
- 100% free and accurate
Conclusion
The Flow Rate Calculator you are using right now is trusted by engineers, technicians, and students worldwide. Bookmark this page and use it every time you need fast, reliable flow calculations. Design better, faster, and with complete confidence!