Flow Rate Calculator: Measure Water Flow Instantly
Calculate flow rate, velocity, and pipe capacity in L/min, GPM, and m³/h. Essential for plumbers, heating engineers, and homeowners. 100% free, no sign-up.
Calculations
Accuracy
Trusted by pros
Flow Preview
25mm pipe @ 1.5 m/s → ~44 L/min
What Is The Flow Rate Calculator?
Incorrect flow rate estimation leads to undersized pipes, poor water pressure, and system failures. Our flow rate calculator uses pipe diameter and velocity to deliver precise flow rates in multiple units — helping you design efficient plumbing systems.
Avoid pressure issues
L/min, GPM, m³/h
Right pipe sizing first time
💧 Flow Rate Tool – Professional Grade
Enter pipe diameter and velocity, then click calculate
Formula: Flow Rate = Cross-sectional Area × Velocity. Ideal for pipe flow calculator, water pipe sizing, and system design.
Why Professionals Love Our Flow Tool
Instant Flow Rate
L/min, GPM, m³/h — one click.
Auto Unit Conversion
Metric/imperial seamless.
Mobile Optimised
Use on-site anywhere.
100% Free
No signup, unlimited.
System Design
Perfect for heating & water supply.
Pipe Sizing Aid
Determine correct diameter.
How It Works
Enter diameter
In mm or inches
Enter velocity
m/s or ft/s
Click calculate
Instant processing
Get results
L/min, GPM, m³/h
Key Benefits of Accurate Flow Rate
Faster Work
No manual formulas
Unmatched Accuracy
Eliminate guesswork
Saves Money
Right pipe sizing
Avoid Mistakes
Prevents low pressure
Professional Results
Accurate system design
Trusted by Homeowners & Industry Experts
🏠 Homeowners
- Check shower flow rate
- Plan garden irrigation
- Boiler flow assessment
- Avoid pressure drops
- Compare plumber quotes
🔧 Plumbers
- System balancing
- Pipe sizing verification
- Pump selection
- On-site flow estimates
- Professional reports
🏗️ Contractors
- Large scale pipe networks
- Water demand calculation
- Fire sprinkler systems
- Reduce rework
- Accurate bids
🧰 DIY Enthusiasts
- Garden hose flow
- Rainwater systems
- Home plumbing checks
- Learn flow principles
- Double-check pro work
Why Choose Speedy Jet Plumbers?
Real Plumbing Experts
20+ years experience
Local Service Trust
Rapid London & UK coverage
Fast Response
Same-day emergency
Affordable Pricing
Transparent quotes
Free Tools + Services
Empowering customers
Need Professional Plumbing Help?
From flow issues to complete pipe installations — our certified plumbers are ready. Call now for emergency or free estimate.
24/7 Emergency Service – Burst pipes, low pressure & heating failures