In short: the most accurate way to find your garden hose's flow rate is to time how long it takes to fill a container of known volume — a 5-gallon bucket in about 25 seconds works out to 12 GPM. Without a bucket handy, a typical 5/8-inch hose on 40–60 psi city water delivers roughly 9–17 GPM, depending on hose length and diameter. Use the calculator above for either method.
The estimate mode is a planning aid based on hose friction alone. Nozzles, nozzle settings, kinks and worn connectors all reduce real-world flow below the estimate.
How to calculate garden hose flow rate
There are two honest ways to answer "how many GPM does my hose put out?" — measure it directly, or estimate it from the hose's dimensions and your water pressure.
Worked example (bucket method). A 5-gallon bucket fills in 25 seconds. 25 seconds is 25 ÷ 60 = 0.4167 minutes. 5 gallons ÷ 0.4167 minutes = 12.0 GPM — the calculator's default result.
Without a bucket on hand, the calculator's estimate mode treats the length of hose like a length of pipe and solves the Hazen-Williams friction equation for the flow that would use up your entire supply pressure as friction loss by the time the water reaches the open end:
Worked example (estimate method). 50 psi converts to about 115.3 ft of head. For a 5/8-inch (0.625 in) hose, 50 ft long, C = 130 (standard vinyl/rubber), solving the equation above gives Q ≈ 16.7 GPM, exiting at roughly 17.5 ft/s. That is the calculator's default estimate-mode result.
Why the two methods disagree. The estimate models only the hose's own friction — it assumes a fully open end with no nozzle, sharp bends or worn fittings. Real hoses almost always measure lower with the bucket method because of those extra restrictions, which is why the bucket test is the one to trust when you need an exact number.
Why diameter, length and pressure change the answer
Diameter matters most. Flow rises with roughly the 2.63 power of inside diameter in the Hazen-Williams relationship, so a 3/4-inch hose carries substantially more water than a 1/2-inch hose at the same pressure and length — often two to three times as much.
Length works against you. Friction loss accumulates along the entire run, so doubling hose length from 25 to 50 ft can cut flow by roughly a third at the same diameter and pressure. Coiling several hoses together to reach a far corner of the yard costs more flow than it might seem.
Pressure has a smaller effect. Flow rises only with the square root of pressure, so going from 40 psi to 60 psi — a 50% increase in pressure — raises flow by only about 22%. A bigger hose almost always beats a bigger pump.
Reference: estimated flow rate by hose size & length
Estimated GPM at 50 psi supply pressure, standard vinyl/rubber hose (C = 130). Every value matches what the calculator's estimate mode returns for the same inputs.
| ID | 25 ft | 50 ft | 75 ft | 100 ft |
|---|---|---|---|---|
| 1/2 in | 13.51 | 9.29 | 7.47 | 6.39 |
| 5/8 in (most common) | 24.30 | 16.71 | 13.43 | 11.49 |
| 3/4 in | 39.25 | 26.99 | 21.69 | 18.57 |
| 1 in | 83.63 | 57.52 | 46.21 | 39.56 |
Worked examples
5-gallon bucket test
12.0 GPM
A 5-gallon bucket fills in 25 seconds — the calculator's measured-mode default. This is the number to trust for your actual hose, nozzle and pressure.
50 ft of 5/8-inch hose, 50 psi
16.7 GPM
Estimated from hose friction alone (standard hose, C = 130): about 16.7 GPM at roughly 17.5 ft/s exit velocity — before any nozzle restriction.
Same hose, doubled to 100 ft
11.5 GPM
Doubling the run from 50 to 100 ft at the same diameter and pressure cuts the estimated flow by roughly a third, from 16.7 to about 11.5 GPM.
What else affects real-world flow
Nozzles and sprayers. Any shutoff nozzle or spray head adds its own restriction on top of the hose's friction loss — a narrow "jet" or "shower" setting cuts flow well below what a fully open end would deliver.
Kinks and coils. A sharp kink can partially or fully block flow, and tightly coiled hose adds extra bend losses the straight-pipe estimate does not capture.
Connector and washer condition. A worn or partially seated washer at the spigot or nozzle connection restricts flow and can also cause a leak that wastes water without adding to what reaches the nozzle.
Time-of-day pressure swings. Municipal pressure often dips during peak demand — typically early morning and evening — so a hose can measure a few GPM lower at those times than at midday.
Frequently asked questions
What is a typical garden hose flow rate?
Most residential garden hoses deliver somewhere between about 9 and 17 GPM (gallons per minute), depending on the hose's inside diameter, its length, and household water pressure, which typically runs 40–60 psi. A standard 5/8-inch hose is usually toward the middle of that range; a wider 3/4-inch hose or a shorter run delivers more.
How do I measure my garden hose's actual flow rate?
The most accurate way is the bucket method: time how long it takes to fill a container of known volume — a 5-gallon bucket is the classic choice — then divide the volume by the time in minutes. This captures the real effect of your specific hose, connectors, kinks and nozzle, which a theoretical estimate cannot.
Does a longer hose reduce flow rate?
Yes, noticeably. Friction loss increases with hose length, so a 100-foot hose delivers meaningfully less flow than a 25-foot hose of the same diameter at the same supply pressure — often 40% or more of a reduction between those two lengths, based on the Hazen-Williams friction relationship.
Does a spray nozzle reduce the flow rate?
Yes. Any nozzle, sprayer or shutoff valve adds its own restriction on top of the hose's own friction loss, and a narrow spray pattern restricts flow more than a wide, fully open setting. This calculator's estimate mode models the open hose end only; a nozzle in place will read lower on an actual bucket test.
What water pressure do most homes have?
Most U.S. municipal water utilities deliver residential service in the 40–60 psi range, with 50 psi a common planning figure. Pressure varies by elevation, distance from the water main, time of day and whether a pressure-reducing valve is installed, so actual household pressure can run higher or lower.
Does hose diameter matter more than water pressure?
Generally yes. Flow rate rises with roughly the 2.63 power of diameter under the Hazen-Williams relationship (since diameter enters through the pipe area as well as the friction term), but only with the square root of pressure. Moving from a 1/2-inch to a 3/4-inch hose typically raises flow far more than a modest pressure increase would.
Sources & references
- Williams, G. S., & Hazen, A. (1933). Hydraulic Tables (3rd ed.). John Wiley & Sons.
- American Water Works Association (AWWA). Manual M22: Sizing Water Service Lines and Meters.
John Mac, PE
Water Systems Specialist · Austin, Texas
Texas-licensed Professional Engineer with 13+ years in residential water systems and 180+ completed projects. Writes and reviews the calculators on watercalculator.us. Read full bio
Texas PE (2016) · BS Civil Engineering, Hydraulics (2013)