Garden Hose Flow Rate Calculator
Calculate garden hose flow rate in GPM from diameter, length, and water pressure.
Compare 1/2, 5/8, and 3/4-inch hoses and estimate fill time for pools.
Garden hose flow rate is the volume of water delivered per minute. It depends on your home’s water pressure, the hose’s internal diameter, and the total length of the hose run. Friction loss, the resistance of water dragging along the hose wall, rises with length and falls sharply with diameter.
The relationship, in the form this page uses:
Flow = Base flow × √(Pressure ÷ 40) × √(50 ÷ Length in feet)
Both square roots matter. Doubling your pressure does not double the flow, it multiplies it by about 1.4. Doubling the length does not halve the flow either, it cuts it to about 71%. That is why a long hose is less of a disaster than people expect, and why a bigger pump is less of a fix.
Flow rate reference table at 40 PSI (typical residential supply):
| Hose Diameter | 25 ft / 7.6 m | 50 ft / 15 m | 100 ft / 30 m | 150 ft / 46 m |
|---|---|---|---|---|
| 1/2" (13 mm) | 8.5 GPM / 32 LPM | 6.0 GPM / 23 LPM | 4.2 GPM / 16 LPM | 3.5 GPM / 13 LPM |
| 5/8" (16 mm) | 17.0 GPM / 64 LPM | 12.0 GPM / 45 LPM | 8.5 GPM / 32 LPM | 6.9 GPM / 26 LPM |
| 3/4" (19 mm) | 26.9 GPM / 102 LPM | 19.0 GPM / 72 LPM | 13.4 GPM / 51 LPM | 11.0 GPM / 42 LPM |
There is a ceiling the formula does not know about. A very short hose on very high pressure runs off the end of any friction model, and the answer stops being physical: the bore, the tap and the couplings choke the flow long before the arithmetic runs out. This calculator caps each size at what it can actually pass, roughly 12 GPM for 1/2 inch, 22 for 5/8 and 34 for 3/4.
Residential water pressure ranges:
- Low pressure: 20–40 PSI
- Normal: 40–60 PSI (most homes)
- High pressure: 60–80 PSI
- Above 80 PSI: may damage appliances: install a pressure regulator
Water usage applications and flow requirements:
| Use | Required Flow |
|---|---|
| Drip irrigation | 0.5–2 GPM |
| Soaker hose | 1–3 GPM |
| Hand watering | 2–5 GPM |
| Lawn sprinkler | 4–10 GPM |
| Pressure washer (residential) | 2–4 GPM at higher PSI |
| Filling a 5-gal bucket | Any rate, so time it for an actual GPM figure |
Choosing the right hose diameter:
- 1/2": Suitable for small container gardens and light hand watering
- 5/8": The most popular size, covers most residential gardening needs
- 3/4": Best for large gardens, long runs, or when feeding multiple sprinklers simultaneously
Water quantity formulas:
Gallons used = Flow Rate (GPM) × Minutes
Liters used = GPM × Minutes × 3.785
Worked example: A 5/8" hose, 75 ft long, watering for 20 minutes at 50 PSI.
- Base flow for 5/8" at 40 PSI over 50 ft: 12 GPM
- Pressure: √(50 ÷ 40) = 1.118
- Length: √(50 ÷ 75) = 0.816
- Flow = 12 × 1.118 × 0.816 = 11.0 GPM
- Water used = 11.0 × 20 = 219 gallons (829 liters)
Metered water in the US runs somewhere between $0.002 and $0.012 per gallon depending on the utility, so that session costs roughly 45 cents to $2.60. Check your own bill, because the spread between cheap and expensive districts is wider than most people assume and it is the only figure that matters for your garden.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.