How much soaker hose or how many sprinklers do I need?
There are two easy ways to water a bed or lawn, and they're sized differently. A soaker hose weeps water along its length, so you size it by how much hose it takes to snake through the bed. A sprinkler throws water over a circle, so you size it by how many you need to cover the area. Pick a method above and the calculator handles the rest — including the run time to apply your target amount and the water it uses.
Both share one number: it takes about 0.623 gallons to lay one inch of water over one square foot. So an inch over 1,000 sq ft is about 623 gallons, whichever way you deliver it.
Soaker hose: length and spacing
Lay soaker hose in parallel runs and connect them with solid hose or a manifold at one end. How far apart the runs go depends on your soil, because water spreads sideways differently:
| Soil | Run spacing | Why |
|---|---|---|
| Sandy | ~12 in | Water drops nearly straight down — keep runs close |
| Loam | ~18 in | Moderate sideways spread |
| Clay | ~24 in | Water wicks far sideways — runs can be wider |
The hose length is roughly your bed area ÷ run spacing. Keep any single run under about 100 ft — beyond that, pressure drops and the far end barely drips, so split a big bed into several runs fed from a splitter. Soaker output is pressure-dependent (often around 0.5 GPH per foot at low pressure); lower your house pressure with a regulator for even, slow soaking.
Sprinklers: coverage and run time
A sprinkler covers a circle of about π × radius² — a head that throws 15 ft covers roughly 700 sq ft. Divide your lawn by that for the number of positions. For even coverage, overlap the spray head-to-head (space heads about one radius apart); it uses more heads than the bare circle math suggests but kills the dry rings between them.
Run time comes from the precipitation rate — how fast the sprinkler lays down water:
Precip rate (in/hr) = 96.3 × flow (GPM) ÷ area covered (sq ft)
Most oscillating and hose-end sprinklers only manage 0.2–0.5 in/hr, so applying a full inch can take two to four hours per spot. Don't trust the clock alone — do the tuna-can test: set a few straight-sided cans around the spray, run the sprinkler, and time how long it takes to collect one inch. That's your true run time.
How much water — and watering smart
Lawns and most beds want about 1 inch of water per week, including rain. Deliver it in one or two deep soakings rather than daily sprinkles — deep watering drives roots down and builds drought tolerance. Tips that save water and plants:
- Water at dawn. Early morning means less evaporation and wind drift than midday, and drier leaves overnight than evening watering.
- Put it on a timer. A hose-bib timer runs the cycle at the right time automatically — set it and forget it.
- Soaker and drip beat sprinklers for beds. They put water at the roots with almost no evaporation or runoff, using far less than overhead spray.
- Watch for runoff. If water sheets off before an inch soaks in (common on clay or slopes), split the run time into shorter cycles with soak-in breaks.
- Adjust for weather. Skip a cycle after good rain, and add time in heat waves. A rain gauge tells you what nature already gave you.