Garden Hose Length and Flow Calculator
Work out what hose you actually need before you buy one. Put in the distance from your tap to the far end of the garden, pick what you use the hose for, and this tool tells you the length to buy, the diameter that will carry enough water, and whether a 100 ft hose will leave your sprinkler flat.
How the numbers work
Nothing here is a guess dressed up as a formula. The tool uses four things you can check yourself:
- Friction loss. Water rubbing against the hose wall costs pressure. At 5 gallons a minute, roughly 12 psi per 100 ft in a 1/2 inch hose, 5 psi in 5/8 inch, and 2 psi in 3/4 inch. Loss rises with flow, so a bigger job costs more.
- Length. Loss is proportional: 100 ft costs about twice what 50 ft costs, at the same flow.
- Elevation. About 0.43 psi per foot of rise. A hose running up a slope or to a second storey pays that toll whatever its diameter.
- What the job needs. Hand watering works on 15 psi at the end; a sprinkler wants 25; a pressure washer wants 35. Below that, the far end of the hose goes flat.
Tap pressure is assumed to be 50 psi unless you change it, which is typical for a North American home. Flow estimates assume a clean hose, a fully open tap and no leaking washers - a worn washer can cut flow noticeably and no calculator will see it.
What the answer means
If the tool says your chosen diameter will not hold the pressure your job needs, you have three options, in order of cost: shorten the run, move up a diameter, or split the job into two shorter runs from the same tap at different times. Buying the longest hose on the shelf makes all three worse, because every extra foot adds friction you cannot get back.
Two practical notes. First, a hose that is 100 ft long is not the same hose as two 50 ft lengths joined - the joined run behaves like a 100 ft hose, so the same numbers apply. Second, if your tap runs two lines at once, each one gets roughly half the flow, which is why a sprinkler that worked alone goes weak when someone fills a paddling pool.
Common questions
Is a longer hose always worse? For pressure, yes at the same diameter - every foot of length costs pressure. But a hose that does not reach is useless, so buy the shortest length that covers the garden and no more.
What diameter should I buy? 5/8 inch is the usual sweet spot for home use. Go to 3/4 inch for long runs or a pressure washer, and keep 1/2 inch for short hand-watering runs and light hoses.
Why does my sprinkler pulse or go flat? Almost always pressure at the far end dropping below what the head needs - either the run is too long for the diameter, or a second tap is open.
Does an expandable hose change the maths? It does, because the inner tube is narrow. An expandable hose moves less water than a 5/8 inch rubber hose of the same stated length, so treat it as the next size down for flow purposes. It is a hand-watering hose, not a sprinkler main.
If the answer came out at 50 ft in 5/8 inch, that is the hose we make: the Grafork reinforced expandable garden hose - light enough to carry, and honest about being a hand-watering hose.