Calculate Litres Per Minute (LPM) using the bucket method.
Size of the bucket or container used.
How long it took to fill the container.
Flow Rate: 0 Litres/Minute
Litres Per Hour0
Gallons Per Minute (US)0
Litres Per Second0
Cubic Meters / Hour0
How to Calculate Water Flow Rate (Litres Per Minute)
Understanding your water flow rate is essential for selecting the right plumbing fixtures, designing irrigation systems, or troubleshooting water pressure issues. The flow rate determines how much water comes out of your tap, shower, or hose pipe over a specific period.
The Bucket Method
The most accurate and simple way to measure flow rate at home is the "Bucket Method." You don't need expensive equipment—just a container of known volume (like a standard 9-litre or 10-litre bucket) and a stopwatch (or your smartphone).
The Formula:
To calculate Litres Per Minute (LPM), use the following formula:
Flow Rate (LPM) = (Container Volume in Litres / Time in Seconds) × 60
Step-by-Step Guide
Prepare the Container: Get a bucket or jug. Ensure you know exactly how many litres it holds.
Prepare the Timer: Open the stopwatch app on your phone.
Start the Flow: Turn the tap or shower on fully. Let it stabilize for a few seconds.
Measure: Place the container under the water flow and start the timer simultaneously.
Stop: Stop the timer the exact moment the water reaches the target volume level or the bucket overflows (if you know the full bucket volume).
Calculate: Input your volume (Litres) and time (Seconds) into the calculator above.
Typical Flow Rates for Home Fixtures
Comparing your results to standard averages can help you identify if you have low pressure or if your fixtures are water-efficient.
Fixture Type
Standard Flow Rate (LPM)
Water Efficient (LPM)
Kitchen Tap
15 – 20 LPM
6 – 9 LPM
Shower Head
9 – 15 LPM
7 – 9 LPM
Bathroom Basin Tap
10 – 15 LPM
4 – 6 LPM
Garden Hose (Standard 1/2″)
20 – 30 LPM
N/A
Bathtub Faucet
20 – 30 LPM
N/A
Why is Flow Rate Important?
Combi Boilers: Combination boilers require a minimum flow rate to activate the heating element. If your flow is too low, you may not get hot water. Conversely, they have a maximum output; knowing your flow rate helps size the boiler correctly.
Irrigation: Sprinkler systems require specific flow rates and pressures to cover the desired area effectively.
Water Conservation: Knowing your current usage helps in installing flow restrictors or eco-shower heads to save on water and energy bills.
function calculateFlowRate() {
// 1. Get DOM elements
var volumeInput = document.getElementById('containerVolume');
var timeInput = document.getElementById('timeToFill');
var resultBox = document.getElementById('resultBox');
var errorMsg = document.getElementById('errorMsg');
// 2. Get values
var volume = parseFloat(volumeInput.value);
var seconds = parseFloat(timeInput.value);
// 3. Reset error state
errorMsg.style.display = 'none';
errorMsg.innerHTML = ";
resultBox.style.display = 'none';
// 4. Validate inputs
if (isNaN(volume) || volume <= 0) {
errorMsg.innerHTML = "Please enter a valid container volume greater than 0.";
errorMsg.style.display = 'block';
return;
}
if (isNaN(seconds) || seconds <= 0) {
errorMsg.innerHTML = "Please enter a valid time greater than 0.";
errorMsg.style.display = 'block';
return;
}
// 5. Calculation Logic
// Formula: (Volume / Time in Seconds) * 60 = Litres Per Minute
var lpm = (volume / seconds) * 60;
// Derived calculations
var lph = lpm * 60; // Litres per hour
var gpm = lpm * 0.264172; // US Gallons per minute
var lps = lpm / 60; // Litres per second
var m3h = lph / 1000; // Cubic meters per hour
// 6. Format and Display Results
document.getElementById('resLPM').innerText = lpm.toFixed(2);
document.getElementById('resLPH').innerText = lph.toFixed(1);
document.getElementById('resGPM').innerText = gpm.toFixed(2);
document.getElementById('resLPS').innerText = lps.toFixed(3);
document.getElementById('resM3H').innerText = m3h.toFixed(3);
// Show result box
resultBox.style.display = 'block';
}