Quickest way to estimate paddock area in the field?

Measure long and short sides in metres, multiply and divide by 10,000. A 1 km x 500 m paddock = 50 ha. For irregular shapes, break into rectangles and triangles.

How accurate does area measurement need to be?

For expensive inputs at $400/ha on 200 ha, a 2% area error = $1,600 over or under. GPS mapping achieves < 0.5% accuracy. Tape measurements on regular paddocks achieve 1-3%.

My property is in acres on the title - how to convert?

Multiply acres by 0.4047. 320 acres = 129.5 ha. 640 acres (1 square mile) = 259 ha.

Paddock Area Calculator — Free Agriculture Calculator

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The agronomist is waiting on individual paddock areas before he can write the variable-rate fertiliser prescription. You have the dimensions in the field notes — you need hectares before his laptop comes out.

Paddock Area Calculator

Land

Paddock shape

Length (m)

Imperial: enter feet

Width (m)

1 hectare = 10,000 m² = 2.471 acres Rectangle: L × W · Triangle: Heron's formula · Circle: π × r² Common paddock conversions: 1 km × 1 km = 100 ha · 1 mile × 1 mile = 640 acres (1 section)
For irregular paddocks, divide into rectangles and triangles and add the results.

Reference: Geoscience Australia — Land Measurement

ℹ️ Results are estimates for planning purposes. Verify with current standards and a qualified professional.

1 What this calculator does

Calculates paddock area in hectares, acres and square metres from measured dimensions. Supports rectangular, triangular, and composite paddock shapes. Converts between hectares and acres. Calculates perimeter for fencing estimates.

2 Formula & professional reasoning

Rectangle (ha) = Length (m) x Width (m) / 10,000
Triangle (ha) = 0.5 x Base (m) x Height (m) / 10,000
1 ha = 2.471 acres  |  1 acre = 0.4047 ha

Accurate paddock area is the foundation of all per-hectare input calculations. A 5% area error on a 200 ha paddock means ordering 10 ha worth of fertiliser too much or too little. At $400/ha input cost, that is a $4,000 error per paddock. GPS walk-the-boundary is most accurate for irregular shapes; physical measurements are adequate for regular paddocks.

3 Worked examples

⚠️ Illustrative example only — not clinical or professional instruction.

Basic

Rectangular cultivation paddock

Given: Length: 1,240 m Width: 780 m

Working: Area: 1,240 x 780 = 967,200 m2 / 10,000

Answer: 96.7 ha

💡 Perimeter: 2 x (1,240 + 780) = 4,040 m of fence line.

Standard

Triangular paddock with diagonal road boundary

Given: Enclosing rectangle: 80 ha Corner triangle to subtract: Base 600 m x Height 450 m

Working: Triangle: 0.5 x 600 x 450 = 135,000 m2 = 13.5 ha Net: 80 - 13.5

Answer: 66.5 ha

💡 For paddocks with diagonal boundaries: calculate the enclosing rectangle then subtract corner triangles.

Advanced

Convert purchased block from acres

Given: Block advertised as 650 acres

Working: 650 x 0.4047

Answer: 263 ha

💡 Always convert to ha before applying metric kg/ha input rates. Mixing acres with ha rates creates 2.47x errors.

4 Sanity check

Quick mental reference points

1 km x 1 km = 100 ha | 1 km x 500 m = 50 ha | 500 m x 500 m = 25 ha

Typical paddock sizes

Broadacre cropping: 50-200 ha | Irrigation blocks: 5-50 ha | Grazing paddocks: 50-500 ha

GPS mapping accuracy

Walk-the-boundary GPS: +/- 0.1-0.5 ha for large paddocks

Better than tape-measured dimensions for irregular paddocks.

Perimeter for fencing

2 x (L + W) for rectangles | Add 10-15% for gates and corners

5 Common errors

Error	Cause	Consequence	Fix
Entering dimensions in km instead of metres	Reading GPS distances in km	Area result 1,000,000x too large	Convert km to metres: 1.24 km = 1,240 m.
Using gross area instead of net cropped area	Not subtracting non-cropped areas	Inputs applied across headlands, dams and laneways	Subtract headlands (5-10%), in-paddock dams, tree lines and hard standing for input calculations.
Not updating area after paddock subdivision	Using old paddock map	Wrong area used for years of input calculations	GPS re-map every paddock after any boundary change.
Mixing acres and hectares in rate calculations	Using overseas rate recommendations in ac without converting	Application rate off by 2.47x	Confirm whether a recommendation is kg/ha or kg/ac before applying.