Land measurement starts with the sides of your plot. This land area calculator works out the area of a plot with 4 sides, a triangle or an irregular shape, and then shows it in square feet, gaj, cent, guntha, bigha, acre and other units.
Step 1: measure the plot
- Use a long tape. Measure every side in feet (or metres) and write it down in order: side A, B, C, D.
- For a plot with 4 unequal sides, also measure one diagonal, from one corner to the opposite corner. Without a diagonal, the area of an uneven 4 sided plot cannot be found exactly.
- Note any bends. A bent side should be treated as two sides.
Step 2: pick the right formula
Rectangle or square
Area = length x width. A plot of 40 ft by 60 ft is 2,400 sq ft.
Triangle (Heron's formula)
If the sides are a, b and c, first find s = (a + b + c) / 2. Then area = square root of s x (s minus a) x (s minus b) x (s minus c).
Example: sides of 45 ft, 52 ft and 60 ft. s = 78.5. Area = square root of 78.5 x 33.5 x 26.5 x 18.5 = about 1,135.44 sq ft.
4 sides, unequal (land area calculator 4 sides)
Split the plot into two triangles along the diagonal, find each with Heron's formula and add them.
Example: sides A = 60 ft, B = 40 ft, C = 62 ft, D = 38 ft, and the diagonal that separates sides A and B from sides C and D is 72 ft. Triangle 1 has sides 60, 40, 72: area about 1,199.99 sq ft. Triangle 2 has sides 62, 38, 72: area about 1,177.71 sq ft. Total: about 2,377.71 sq ft.
Many people use a shortcut: average of opposite sides multiplied together. Here that gives (60 + 62) / 2 x (40 + 38) / 2 = 2,379 sq ft. The shortcut is exact only for rectangles and can be wrong for slanted plots, so use the diagonal method when money is involved.
Irregular plot
Break the shape into triangles and rectangles, find each area and add them. The more pieces you use, the closer the answer.
Step 3: convert to your local unit
Take the 4 sided example of about 2,377.71 sq ft:
- Gaj: 264.19 (divide by 9)
- Square metres: 220.9
- Cent or decimal: 5.46 (divide by 435.6)
- Guntha: 2.1834 (divide by 1,089)
- Acre: 0.0546
- West Bengal katha: 3.3; Patna katha: 1.75
- Standard marla: 8.73
Land measurement units table
| Unit | Square feet | Note |
|---|---|---|
| Gaj (square yard) | 9 | fixed |
| Square metre | 10.7639 | fixed |
| Cent, decimal, satak | 435.6 | fixed, 1/100 acre |
| Are | 1,076.39 | fixed, 100 sq m |
| Guntha | 1,089 | fixed, 1/40 acre |
| Kanal | 5,445 | Punjab, Haryana |
| Acre, killa | 43,560 | fixed |
| Hectare | 107,639.1 | fixed, 100 are |
| Katha | 600 to 3,267 | varies by region |
| Bigha | 6,804 to 65,340 | varies by region |
For Telugu speaking areas, house sites are measured in square yards and ankanam, and farm land in acres, guntas and cents.
About GPS and walking apps
Phone apps that measure land by walking the boundary or tapping a map are handy for a rough idea. Phone GPS can drift by several metres, which matters on a small plot. For buying, selling or dividing land, measure with a tape and check against the land record and the official survey map.
Tips
- Measure in one unit only. Do not mix feet and metres.
- Write down sides in order around the plot so the diagonal is between the right corners.
- For a sale, partition or court matter, get the plot measured by the local surveyor, amin or patwari and check the land record.
Need only a room or simple plot? Try the square feet calculator.
Questions people ask
How do I calculate land area with 4 unequal sides?
Measure all four sides and one diagonal. The diagonal splits the plot into two triangles. Find each with Heron's formula and add them. The average of opposite sides method is only a rough shortcut.
How to calculate land area in square feet?
Measure each side in feet. For a rectangle, multiply length by width. For other shapes, split into triangles and rectangles, find each area and add them.
What is the land measurement formula for a triangle?
Use Heron's formula. Add the three sides and halve the total to get s. Multiply s by (s minus each side) and take the square root.
Is a land measurement app accurate?
Apps using phone GPS give a rough idea only, because the position can drift by several metres. Use a tape measure and the land record for any legal or money matter.
Which land measurement units are fixed?
Gaj, square metre, cent, decimal, are, guntha, acre and hectare are fixed. Bigha, katha, biswa and dhur change by region, so check the local value.
Local units can differ inside a state. Before a sale, partition or court filing, confirm the unit with your tehsil, circle or revenue office and check the land record. How we check our numbers.