Garden Hose Diameter to Flow Rate Converter

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:

All the figures below are at 40 PSI on a 50 to 100 foot run, with nothing screwed on the end.

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. Expect about 3 to 5 GPM (11 to 17 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 to 10 GPM (25 to 36 L/min). 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 to 17 GPM, or 45 to 64 L/min) 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. The hose itself can pass roughly 19 to 28 GPM (72 to 105 L/min), though see the note below on what your spigot will actually give you. Used for large sprinkler systems, commercial watering, and filling big pools or tanks. These hoses are heavier and stiffer than 5/8-inch hoses.

1 inch (25.4 mm) ID: Commercial and agricultural grade. On paper it will pass 40 GPM and up (150 L/min), which is well beyond anything a house can supply. Used for irrigation, farm equipment, and industrial applications, and rarely seen in residential settings because of the weight and bulk.

Why the hose is often not the limit. A standard 3/4 inch hose bib fed by ordinary household plumbing delivers somewhere around 12 GPM at 40 PSI, rising to about 17 at 80 PSI. That ceiling belongs to the tap and the pipe behind it, not to the hose, so once you are past 5/8 inch on a short run you are buying stiffness and weight for no extra water. It is the real reason 5/8 inch became the default size in North America rather than 3/4. On a well pump, a farm standpipe or a long run where friction dominates, the wider hose earns its keep.

The flow rate formula: Flow rises faster than the cross-sectional area, roughly with diameter to the power 2.6, because a wider hose has less wall friction per unit of water carried. Going from 1/2 inch to 5/8 inch is worth about 80 percent more flow, and doubling the diameter multiplies it about sixfold.

The calculator above uses the Hazen-Williams equation, the standard water-pipe formula, solved for flow when all of the supply pressure is spent on friction in the hose:

Head loss (ft) = 10.44 x L x Q^1.852 / (C^1.852 x d^4.8655) Where Q = flow (GPM), L = length (feet), d = inner diameter (inches), and C = 150 for smooth rubber or vinyl hose. Pressure converts to head at 2.31 feet per PSI.

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.