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How to figure out how many acres a field is, including a center pivot

Measure the field in feet, work out the area in square feet, and divide by 43,560. A 660 by 330 ft field is 217,800 sq ft, which is exactly 5 acres. A pivot with a 1,320 ft radius covers 125.66 acres.

3 min read · Updated 2026-09-07

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Why acreage matters for spraying

Product for a job is the label rate times the acres you treat. Guess the acres and you either run short halfway through a field or mix product you then have to deal with. A measured area gives you the right number of tank loads before you start.

The formulas for common field shapes

  • Rectangle: length × width
  • Circle or center pivot: π × radius²
  • Triangle: ½ × base × height
  • Acres = square feet ÷ 43,560; hectares = square metres ÷ 10,000

Calculate acreage in SprayMaster

  1. Open Area / Acreage from Pro Calculators (it needs SprayMaster Pro).
  2. Choose Units: feet and acres in US, metres and hectares in Metric.
  3. Under Field, pick the Shape: Rectangle, Circle / Pivot or Triangle.
  4. Type the dimensions you measured: Length and Width, Radius, or Base and Height.
  5. Read the Result: square feet (or m²) and Acres (or Hectares).

Worked examples

Area / Acreage results
ShapeMeasuredAreaAcres or hectares
Rectangle660 × 330 ft217,800 ft²5 acres
Circle / PivotRadius 1,320 ft5,473,911 ft²125.66 acres
TriangleBase 400 ft, height 300 ft60,000 ft²1.38 acres
Rectangle (metric)200 × 150 m30,000 m²3 ha

How many acres does a center pivot cover?

It depends on the radius the pivot actually wets, measured from the pivot point to the end of the spray — a 1,320 ft radius covers 125.66 acres. The app treats the pivot as a plain circle and does not add end-gun reach or corner systems. Measuring a shade short and underestimating is safer than guessing high and running out of product mid-pass.

What about an irregular field?

Split it into rectangles and triangles, calculate each one, and add them up yourself. For example, a 660 × 330 ft rectangle plus a triangle with a 400 ft base and 300 ft height gives 5 + 1.38 = 6.38 acres. The app has no GPS, map drawing or walk-the-boundary measuring, so your measurements set the accuracy.

From acres to a tank plan

Take the acres into the free Tank Mix calculator: turn on Size a whole job and enter the figure as Total Area. At 32 fl oz per acre with a 1,000 gal tank and 15 GPA, the 125.66-acre pivot takes 4,021.12 fl oz and 1.88 tank loads, each tank covering 66.67 acres.

Tips for measuring

  • Measure the sprayed area, not the deed: skip waterways, yards and buffer zones you will not treat.
  • A measuring wheel or a long tape beats pacing; if you pace, calibrate your stride first.
  • Measure the height of a triangle at a right angle to the base, not along a sloping side.

Questions and answers

How do I calculate acreage from feet?
Find the area in square feet and divide by 43,560. A 660 by 330 ft rectangle is 217,800 sq ft, or 5 acres.
Can SprayMaster measure a field with GPS?
No. It calculates acres from dimensions you type for a rectangle, a circle or a triangle. There is no GPS or map measuring.
How many acres is a quarter-mile pivot?
A pivot with a 1,320 ft radius covers 125.66 acres as a full circle. Measure your own wetted radius, since end guns and corners change the real area.
Is Area / Acreage free?
No, it is a SprayMaster Pro feature. The Tank Mix calculator you feed the acres into is free.

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