Calculate center pivot irrigation coverage area from pivot length. Estimate acres irrigated with and without corner systems using π × r².
A center pivot irrigates a circular area defined by the pivot's length (radius). The area of a circle is πr², making a standard quarter-mile pivot (1,320 ft) cover about 125.7 acres of a 160-acre quarter section. The remaining 34.3 acres in the corners are left dryland unless a corner system (swing arm) is installed.
Corner systems extend the pivot's reach into the field corners using an articulated end gun or swing arm, recovering up to 95% of the full quarter section. Knowing the exact irrigated acreage helps you calculate water requirements, seed rates, fertilizer amounts, and crop insurance coverage.
This calculator computes the circular area, the unirrigated corners, and the additional area recovered by a corner system option. Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation. By automating the calculation, you save time and reduce the risk of costly errors in your planning and decision-making process.
Knowing exact irrigated acreage is essential for input costs, water permits, crop insurance, and yield estimation. This tool gives you the precise number you need for planning instead of rough approximations. Having a precise figure at your fingertips empowers better planning and more confident decisions. Manual calculations are error-prone and time-consuming; this tool delivers verified results in seconds so you can focus on strategy.
Circle Area (ft²) = π × r² Circle Area (ac) = π × r² / 43,560 Corner Area = Field Area − Circle Area Corner System Recovery ≈ Corner Area × Recovery %
Result: Circle = 125.7 ac; with corners = 156.6 ac
Circle = π × 1320² / 43,560 = 125.66 ac. Corners = 160 − 125.66 = 34.34 ac. At 90% recovery, corner system adds 30.9 ac, so total irrigated = 156.6 ac.
A quarter section is 1,320 ft × 1,320 ft = 160 acres. A pivot with radius 1,320 ft inscribes a circle covering π × 1320² / 43,560 = 125.66 acres, or 78.5% of the field. The four corner triangles total 34.34 acres (21.5%).
End guns cost $2,000–$5,000 and add 5–10 acres. Corner systems cost $40,000–$80,000 and add 25–32 acres. At $500/acre/year net revenue, a corner system pays for itself in 3–6 years while an end gun pays back in 1–2 years.
Modern corner systems use GPS to track the pivot's position and extend or retract the arm precisely at field boundaries. This maximizes recovery while avoiding application to roads, waterways, or neighboring property.
A 1,320-foot radius pivot covers about 125.7 acres. In a 160-acre quarter section, that leaves 34.3 acres in the corners unirrigated.
A corner system is a swing arm at the end of the pivot that extends into the corners as the pivot rotates. It can recover 85–95% of the corner area, bringing total irrigated area close to 155–158 acres on a quarter section.
The area immediately around the pivot point (typically 20–30 ft radius) does not receive irrigation water. This is a negligible area (< 0.1 acre) for most calculations.
If the field is rectangular or irregular, the pivot radius is limited by the shortest distance from the pivot point to the field boundary. Effective irrigated area may be less than πr² if the circle extends beyond the field.
An end gun is a large sprinkler that extends range by 30–60 ft in all directions. A corner system is a hinged span that only deploys in the corners. Corner systems provide better uniformity than end guns.
Yes. Two half-section pivots or four quarter-circle pivots can irrigate more total area than one full pivot, but infrastructure costs are higher.