Land Area Calculator for Fields
Measure the area of a field from its side lengths – rectangular, triangular or irregular four-sided – in acres, bigha, hectares, guntha and sq ft.
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Please note: Regional land units such as Bigha and Biswa vary between states, districts and sometimes villages. Use these results as a guide and confirm with official land records or your local revenue office for any legal or financial purpose.
Measure your field with a tape, rope or by pacing, and this calculator works out the area in acres, bigha (for your state), hectares, square feet, gaj and guntha. It handles rectangles, triangles and irregular four-sided fields – for the last one, measure one diagonal and the answer is exact.
About the Agricultural Land Area Calculator
Knowing the true area of a field matters for almost every calculation on this site – fertilizer, seed, spray water, irrigation – and for decisions like leasing or buying land. Yet many fields have never been measured properly, and "about 2 bigha" can hide a surprisingly large error.
This calculator works from simple measurements you can take with a measuring tape, a rope of known length or a surveyor's chain:
- Rectangle: length × width.
- Triangle: measure all three sides; the area is calculated with Heron's formula.
- Irregular four-sided field: measure all four sides and one diagonal. The diagonal splits the field into two triangles, each calculated exactly. This avoids the common "average of opposite sides" shortcut, which can overstate the area of skewed fields by 10% or more.
Results are given in acres, hectares, square feet, square metres, square yards (gaj), guntha and cent, along with the perimeter so you can estimate fencing. Pick your state and the area is also shown in bigha – using that state's bigha size, because a bigha in Rajasthan is almost twice the size of one in West Bengal.
Tips for measuring
- Measure along the ground between the actual corner points, keeping the tape straight and tight.
- For fields with more than four sides, divide them into triangles and four-sided parts, calculate each and add them up.
- A karam (used in parts of north India) is taken here as 5.5 ft; local karam lengths can vary.
How to use the Agricultural Land Area Calculator
- 1 Choose the shape of your field.
- 2 Choose the unit you measured in – feet, metres, yards or karam.
- 3 Enter the side lengths. For an irregular four-sided field, label the sides A, B, C, D going around the field, and measure the diagonal between the corner where A meets D and the corner where B meets C.
- 4 Press Calculate.
The formula we use
Rectangle: Area = Length × Width
Triangle (Heron's formula): s = (a + b + c) ÷ 2; Area = √[s(s − a)(s − b)(s − c)]
Four-sided: Area = Triangle(A, B, diagonal) + Triangle(C, D, diagonal)Unit conversions: 1 acre = 43,560 sq ft = 4,046.86 m² = 40 guntha = 100 cent.
Worked example
Rectangular plot: 120 ft × 90 ft = 10,800 sq ft = 0.2479 acre (about 9.9 guntha).
Irregular field measured in metres: sides A = 120, B = 90, C = 100, D = 85 and the diagonal = 140.
- Triangle 1 (120, 90, 140): s = 175, area = √(175 × 55 × 85 × 35) = 5,351 m².
- Triangle 2 (100, 85, 140): s = 162.5, area = √(162.5 × 62.5 × 77.5 × 22.5) = 4,208 m².
- Total = 9,559 m² = 2.362 acres (0.956 ha).
Things to keep in mind
- Measurements must make a real shape. In any triangle, the longest side must be shorter than the other two combined. If not, the calculator will ask you to re-check.
- Slopes. On sloping land, measure horizontally where possible. Measuring along the slope slightly overstates the area.
- For legal purposes use the area on your land record or a licensed surveyor's measurement.
Frequently asked questions
How do I calculate the area of an irregular field?
Measure all four sides and one diagonal. The diagonal divides the field into two triangles; calculate each using Heron's formula and add them. This calculator does it automatically.
Why not just average the opposite sides?
Averaging opposite sides and multiplying is exact only for rectangles. For a skewed field it overestimates the area, sometimes by more than 10%.
How do I measure a field with more than four sides?
Divide it into triangles or four-sided sections using diagonals, calculate each part separately and add the areas.
How many guntha in one acre?
40 guntha make one acre. One guntha is 1,089 sq ft (121 gaj).
What is a karam?
A karam is a traditional measuring length used in parts of north India, commonly 5.5 feet (66 inches). Local values can vary slightly.
Guides that use this calculator
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