How to Use the Hose Size Converter
Garden hoses, washing machine supply lines, and small plumbing fittings are often sized in inches (1/4, 3/8, 1/2, 5/8, 3/4, or 1 inch), which can be hard to picture in metric terms. Select the inch size you're working with, and this converter shows the exact millimeter equivalent along with a rough flow rate you can expect at that size.
Hose sizes are typically measured by inside diameter. A 1/2 inch hose, for example, has an inside diameter of about 12.7mm and delivers roughly 4.5 gallons per minute at typical residential pressure. Larger diameters have less resistance, so more water flows at the same pressure — for tasks like car washing or garden irrigation where flow matters, a 5/8 inch or larger hose is usually the better choice. Keep in mind actual flow depends on your water pressure, hose length, and fittings.
Frequently Asked Questions
It's typically the inside diameter of the hose. A 1/2 inch hose, for example, has an inside diameter of about 12.7mm.
The flow rates shown are rough estimates based on typical residential water pressure (around 40-50 psi). Actual flow depends on your water pressure, hose length, and fittings.