Garden Hose Diameter to Flow Rate Converter
Convert garden hose diameter and water pressure to flow rate in gallons per minute (GPM) and liters per minute.
Covers standard hose sizes from 3/8 to 1 inch.
Select hose diameter and pressure — see the estimated flow rate.
Garden hose flow rate depends on three main factors: the hose inner diameter, the water pressure at the source, and the hose length. A larger diameter and higher pressure produce more flow, while longer hoses reduce flow due to friction losses.
Common garden hose diameters:
3/8 inch (9.5 mm) ID: The smallest standard garden hose size. Used for light-duty watering such as small flower beds, container gardens, and RV connections. At 40 PSI, expect about 3-4 GPM (11-15 L/min). These hoses are lightweight and easy to coil but unsuitable for sprinklers or high-flow attachments.
1/2 inch (12.7 mm) ID: A mid-size hose found in lightweight and expandable hose designs. Delivers about 6-8 GPM (23-30 L/min) at 40 PSI. Adequate for most hand-watering tasks but may struggle to run larger sprinklers at full capacity.
5/8 inch (15.9 mm) ID: The most popular garden hose size in North America. It provides a good balance of flow rate (about 12-17 GPM or 45-64 L/min at 40 PSI) and weight. Suitable for most residential watering needs including sprinklers, car washing, and filling pools.
3/4 inch (19.1 mm) ID: The largest standard consumer garden hose. Delivers approximately 20-25 GPM (76-95 L/min) at 40 PSI. Used for high-flow applications such as large sprinkler systems, commercial watering, and filling large pools or tanks. These hoses are heavier and stiffer than 5/8-inch hoses.
1 inch (25.4 mm) ID: Commercial and agricultural grade. Flow rates can exceed 30 GPM (114 L/min) at typical pressures. Used for irrigation, farm equipment, and industrial applications. Rarely used in residential settings due to weight and bulk.
The flow rate formula (simplified): Flow rate increases with the square of the diameter. Doubling the hose diameter roughly quadruples the flow rate (at the same pressure). This is why upgrading from a 1/2-inch to a 3/4-inch hose makes a dramatic difference.
Approximate GPM = 29.84 x d^2 x sqrt(P) / sqrt(L x f) Where d = inner diameter (inches), P = pressure (PSI), L = length (feet), f = friction factor
Hose length and friction loss: A 25-foot hose loses very little pressure to friction. A 100-foot hose can lose 20-40% of available pressure depending on diameter and flow rate. If you need to run long distances, use the largest diameter hose practical. For runs over 150 feet, consider using 3/4-inch hose.
Pressure considerations: Typical residential water pressure ranges from 30 to 80 PSI (207 to 552 kPa). Most garden hoses are rated for a maximum working pressure of 150-200 PSI and a burst pressure of 400-600 PSI. If your pressure is above 80 PSI, a pressure regulator is recommended to protect hose fittings and attachments.
Hose material and kink resistance: Rubber hoses are the most durable and kink-resistant but heaviest. Vinyl hoses are lightest and cheapest but kink easily and degrade faster in sunlight. Hybrid rubber-vinyl hoses offer a middle ground. Reinforced hoses with mesh or spiral reinforcement resist kinking and maintain flow better when bent.