GardenCalcs.uk
Sprinkler Coverage Calculator — Even Lawn Watering
Work out sprinkler placement and overlap for even lawn coverage.
Longest side of the lawn in metres
Shorter side of the lawn in metres
Pick the closest match. Coverage figures are full-circle at good mains pressure (~2-3 bar); part-circle or low pressure reduces the area.
Usable coverage as a fraction of each head's max area. 0.75 (default) = a light 25% overlap for portable sprinklers; drop toward 0.3-0.5 for professional head-to-head fixed-head spacing.
How We Calculate This
Effective coverage = Sprinkler coverage area × overlap factor (default 0.75, i.e. a 25% overlap allowance).
Sprinklers needed = Lawn area ÷ Effective coverage per sprinkler, rounded up.
Typical full-circle coverage at good mains pressure (~2-3 bar): oscillating ~200 m², gear-drive rotor ~300 m², fixed-spray pop-up ~65 m² (15 ft / 4.6 m radius), impulse ~500 m². Part-circle patterns or low pressure cover less, so size up if in doubt.
The 0.75 default suits portable, moving garden sprinklers (oscillating, impulse) where the spray sweeps the lawn. For a permanent fixed-head system using professional head-to-head spacing — each head reaching its neighbour, one radius apart — overlap is far heavier: drop the overlap factor to around 0.3-0.5 to get a realistic (higher) head count.
Frequently Asked Questions
Sprinklers should overlap by about 25% for even coverage. Without overlap, you get dry patches between sprinkler zones.
Oscillating sprinklers are best for rectangular lawns. Pop-up sprinklers suit smaller areas. Rotary sprinklers are good for medium lawns.
Place a tuna tin on the lawn and time how long it takes to fill 25mm. That is your weekly watering time, split into 2-3 sessions.
Usually yes, but hosepipe bans may restrict use during drought. Check your water company for current restrictions.
For a permanent fixed-head system, the industry standard (Rain Bird, the Irrigation Association) is head-to-head spacing: each sprinkler is placed so its spray reaches the next head — heads sit about one radius apart (50% of the throw diameter) on a square grid, or about 60% on a triangular grid. That is much heavier overlap than the 0.75 default here, so for a designed fixed system lower the Overlap Factor to roughly 0.3-0.5 to get a realistic head count. The 0.75 default is aimed at portable sprinklers you move around the lawn.
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Last updated: February 2026
All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.