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Mastering Liquid Dynamics
Whether you are calculating irrigation needs for a farm, sizing a pump for a pool, or just curious how fast the faucet is running, accurate flow rate conversion is essential. Our tool converts between Imperial (GPM) and Metric (L/min) instantly and even simulates real-world filling scenarios.
Advanced Tool Features
Filling Time
Switch to "Filling Time" mode (⏱️) to calculate how long it takes to fill a Bathtub, Pool, or Olympic Stadium at any given flow rate.
Smart Units
Convert between common units like GPM and L/min, or scientific units like m³/s. We even handle Cubic Feet per Second (cfs).
Real-World Presets
Don't know the numbers? Use our presets for "Shower Head", "Garden Hose", or "Fire Hydrant" to get instant estimates.
How to Use
- Converter Tab: Type a value (e.g. 10 L/min). See the equivalent in GPM or CFS instantly.
- Filling Time Mode: Click the icon.
- Select Container: Choose what you want to fill (e.g., Backyard Pool).
- Results: The tool calculates the exact time (Days, Hours, or Minutes) it will take to fill.
Common Mistakes
- Confusing GPM (US) and GPM (UK).
An Imperial Gallon (UK) is 20% larger than a US Gallon. This tool uses **US Gallons** (3.785 Liters), which is the global standard for pumps.
- Assuming Linear Pressure.
Doubling the pressure does NOT double the flow rate. Flow rate increases with the *square root* of pressure.
Pro Tips
- The "Bucket Test"
The most accurate way to measure measuring flow at home is simply filling a known volume (bucket) and timing it.
- Water Velocity vs Flow.
Velocity is speed (m/s). Flow is volume (m³/s). You can have high velocity in a tiny pipe but very low total flow.
Frequently Asked Questions
What is the flow rate of a typical Garden Hose?
A standard garden hose flows at about 6 to 12 Gallons per Minute (GPM), depending on water pressure and hose diameter. This is roughly 25-45 Liters per minute.
How long does it take to fill a swimming pool?
An average 20,000-gallon pool takes about 24-48 hours to fill with a single garden hose (at 10 GPM). Using a fire hydrant (1000 GPM) would fill it in just 20 minutes!
GPM vs CFM: What's the difference?
GPM (Gallons Per Minute) is for liquids (like water). CFM (Cubic Feet per Minute) is typically for gases (like air in an HVAC system). Be careful not to mix them up.
What is 1 Cubic Meter per Second in L/min?
1 m³/s is equal to 60,000 Liters per minute. That is a massive amount of water—roughly the flow of a small river.
How do I measure flow rate at home?
Use the 'Bucket Method': Get a 5-gallon bucket. Time how many seconds it takes to fill. Divide 5 by the seconds, then multiply by 60 to get GPM.
What flow rate do I need for a shower?
A water-saving showerhead uses 1.5 to 2.0 GPM (6-9 L/min). Older showerheads used up to 5 GPM. Lower flow rates save significant energy on water heating.
Is 'Liters per hour' (L/h) common?
Yes, L/h is often used for very slow flows, like drip irrigation systems or medical IV drips, where precision over a long period is needed.
Why does pipe size affect flow rate?
A wider pipe allows more water to pass through at the same pressure. Doubling the pipe diameter can increase the theoretical flow capacity by 4 times.
What is a 'Fire Flow' test?
It measures the pressure and flow rate (GPM) available at specific fire hydrants to ensure there is enough water to fight a fire in that zone.
What is the flow rate of the Mississippi River?
The average discharge is about 16,792 m³/s (almost 600,000 cubic feet per second). That's enough to fill 6 Olympic swimming pools every single second.