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Guide · 3 worked examples

How to measure a plot and check it against the area on record

Turn the area written on the record into square feet, tape the plot's sides yourself, and compare the two before you rely on a broker's round number.

By Bulan Sarkar · Updated

Quick Answer

First convert the area on the record into square feet with the right state's unit: in West Bengal 1 katha = 720 sq ft and 1 bigha = 14,400 sq ft; a decimal, cent or dismil is 1/100 acre = 435.6 sq ft everywhere; a gaj is a square yard, 9 sq ft. Then tape the plot. A rectangle is length × width. For any four-sided plot, measure all four sides and one diagonal, split it into two triangles and add their areas (Heron's formula, worked below). A 3 katha plot should come to 2,160 sq ft; if your tape gives 2,086 sq ft, the plot is 1.6 chhatak short, and that's worth asking about before anything else.

Source: Directorate of Registration & Stamp Revenue, West Bengal: FAQs, p. 12 (units of land measurement), checked Oct 2026.

720 sq ftin one West Bengal katha
435.6 sq ftin one decimal, cent or dismil (1/100 acre)
4 sides + 1 diagonalenough to measure any four-sided plot
9 sq ftin one gaj (square yard)

Turn the recorded area into square feet

Records and deeds write land in the state's own units, while brokers and builders often talk in square feet or gaj. Before you compare anything, put both in square feet. Some units mean the same thing everywhere because they're fractions of an acre (43,560 sq ft). Others change from state to state, so you need the state's own figure.

Common units and what they are in square feet (government sources, read October 2026)
UnitWhereSq ftSource
KathaWest Bengal, Jharkhand720WB Registration FAQs; DoLR data standard
ChhatakWest Bengal (1/16 katha)45WB Registration FAQs
BighaWest Bengal (20 katha)14,400WB Registration FAQs
Decimal, cent, satak, dismilAll states using it (1/100 acre)435.6DoLR data standard
Gunta, gunthaKarnataka, Maharashtra, Andhra Pradesh (1/40 acre)1,089DoLR data standard; Maharashtra Gazetteer
MarlaHaryana (settled records)272.25Haryana Revenue Department
KanalHaryana (20 marla)5,445Haryana Revenue Department
Gaj (square yard)Everywhere91 yard = 3 ft

A bigha is the unit to be careful with. It's 14,400 sq ft in West Bengal, 9,075 sq ft in Haryana's older records and 17,424 or 27,225 sq ft in Rajasthan depending on the chain the village was surveyed with. Our plot area converter covers nine states and shows the state's own form of the answer. If your state or district isn't on it, ask the local land records office which bigha or katha it uses.

Six land units in square feet, to scaleGaj 9 square feet. Chhatak 45. Marla 272.25. Decimal 435.6. Katha 720. Gunta 1,089.Gaj (square yard)9 sq ftChhatak (West Bengal)45 sq ftMarla (Haryana)272.25 sq ftDecimal, cent or dismil435.6 sq ftKatha (West Bengal)720 sq ftGunta1,089 sq ft
Six land units in square feet, to scale. From the table above. One gunta is exactly 2.5 decimal, and a West Bengal katha is about 1.65 decimal.

Measure the plot with a tape

You need a 30 m (100 ft) steel or fibreglass tape, a helper and pegs at the corners. Pull the tape tight and level, and read it in feet and inches or in metres, but don't mix the two.

For a rectangle, measure both long sides and both short sides. If the two long sides match and the two short sides match, the area is length × width. If they don't match, the plot isn't a true rectangle; treat it as the four-sided case below.

For any four-sided plot, measure all four sides and one diagonal, corner to corner. The diagonal splits the plot into two triangles, and a triangle's area comes straight from its three sides with Heron's formula: work out s, half the perimeter, then area = √(s × (s − a) × (s − b) × (s − c)). Add the two triangles and you have the plot. The second worked example goes through it with real numbers.

For plots with more than four sides, add more diagonals from one corner and more triangles. Curved boundaries need a surveyor.

Measuring a four-sided plot with one diagonal1 peg the four corners A, B, C, D; 2 tape the four sides: AB 40, BC 55, CD 42, DA 52 ft; 3 tape the diagonal AC, 68 ft; 4 triangle ABC with Heron's formula, 1,100 sq ft; 5 triangle ACD, 1,091.3 sq ft; 6 add them, 2,191.3 sq ft, which is 3.04 katha.1Peg the four corners A, B, C and DUse the boundary pillars if they are there2Tape the four sidesAB 40, BC 55, CD 42, DA 52 ft3Tape one diagonal, A to C68 ft4Triangle ABC (40, 55, 68) by Heron's formula1,100.0 sq ft5Triangle ACD (68, 42, 52) by Heron's formula1,091.3 sq ft6Add the two triangles2,191.3 sq ft = 3.04 katha = 5.03 decimal
Measuring a four-sided plot with one diagonal. The numbers are the second worked example: sides 40, 55, 42 and 52 ft, diagonal 68 ft.

Compare the two figures

Now you have the area on record in square feet and the area you taped. Write both down side by side with the difference, in square feet and as a percentage. A tape pulled by hand over 50 ft can be out by a few inches, which is a few square feet on a house plot. A difference of a full unit, a chhatak or more, or a few percent, isn't tape error.

When the figures don't agree, the measurement can't tell you why. The record may be in a different unit from the one you assumed, the boundary pillars may have moved, or the plot may never have matched the paper. That's for the land records office and a licensed surveyor to settle; your numbers only show that there's a question to ask.

The same 3 katha plot: record against tapeOn record: 2,160 square feet. Taped: 2,086.5 square feet.On record: 3 katha2,160 sq ftTaped: 39 × 53.5 ft2,086.5 sq ft
The same 3 katha plot: record against tape. First worked example. The record says 3 katha = 2,160 sq ft; the taped plot is 39 × 53.5 ft = 2,086.5 sq ft, 73.5 sq ft (3.4%) short.

Worked examples

1. A 3 katha plot in West Bengal, taped short

  • On record: 3 katha × 720 sq ft = 2,160 sq ft (a 40 × 54 ft plot would match exactly)
  • Taped: 39 ft × 53.5 ft = 2,086.5 sq ft
  • Difference: 2,160 − 2,086.5 = 73.5 sq ft, or 3.4%
  • In local units: 2,086.5 ÷ 720 = 2.90 katha; 73.5 ÷ 45 = 1.6 chhatak short

Result: The plot is about 1.6 chhatak short of the record. That's well beyond tape error, so take both figures to the land records office and a surveyor.

2. An uneven four-sided plot from sides and a diagonal

  • Sides: AB 40, BC 55, CD 42, DA 52 ft; diagonal AC 68 ft
  • Triangle ABC: s = (40 + 55 + 68) ÷ 2 = 81.5; area = √(81.5 × 41.5 × 26.5 × 13.5) = 1,100.0 sq ft
  • Triangle ACD: s = (68 + 42 + 52) ÷ 2 = 81; area = √(81 × 13 × 39 × 29) = 1,091.3 sq ft
  • Total: 2,191.3 sq ft = 203.6 m² = 3.04 katha = 5.03 decimal

Result: About 2,191 sq ft. Put that number into the plot area converter to see it in your state's units.

3. "200 gaj" in the advert, 4 decimal on the record

  • Advert: 200 gaj × 9 = 1,800 sq ft
  • Record: 4 decimal × 435.6 = 1,742.4 sq ft = 193.6 gaj
  • Difference: 1,800 − 1,742.4 = 57.6 sq ft, or 6.4 gaj

Result: The advert rounds up by 6.4 gaj. Work from the record's 1,742.4 sq ft, and tape the plot to see which figure the ground matches.

Tips and tricks

  • Write down which state's unit the record uses before you convert. A bigha or katha from one state is a different size in another.
  • Measure every side, even on a plot that looks square. Two long sides a foot apart tell you the plot isn't a rectangle.
  • Take the diagonal from the corner that gives two triangles of similar size. Long thin triangles magnify small tape errors.
  • Measure twice, ideally on different days or with a different helper, and use the average.
  • Photograph the tape against each boundary pillar. It's a record of where you measured from.
  • Keep all your working in square feet, then convert once at the end. Converting each side separately piles up rounding.

What we would do

We'd convert the record's area into square feet with the state's own unit, tape all four sides and a diagonal, and work out the area ourselves before talking numbers with anyone. If the tape and the record differ by more than a few square feet, we'd stop there and take both figures to the land records office and a licensed surveyor. The plot buying check puts these steps on one printable sheet, with the asking price worked out per square foot on each area.

Frequently asked questions

How many sq ft is 1 katha?
In West Bengal and Jharkhand, 1 katha is 720 sq ft, so 20 katha make a bigha of 14,400 sq ft. Katha sizes in other states, such as Bihar, differ, so check the state's own figure.
How many sq ft is 1 decimal?
One decimal (also called cent, satak or dismil) is 1/100 of an acre, which is 435.6 sq ft. Some official FAQs round it to 436 sq ft.
How do I calculate the area of an irregular plot?
Measure all four sides and one diagonal, which splits the plot into two triangles. Find each triangle's area from its three sides with Heron's formula, √(s(s−a)(s−b)(s−c)) where s is half the perimeter, and add the two.
Is a gaj the same as a square yard?
Yes. One gaj is one square yard, which is 9 sq ft or about 0.836 m².
My measured area doesn't match the record. What does that mean?
A difference of a few square feet is normal tape error. A larger gap means something needs checking, such as the unit, the boundary or the record itself. The land records office and a licensed surveyor can settle it; a tape measurement can't.

Sources and date checked

This guide covers unit conversion and measuring with a tape. It isn't a survey and says nothing about ownership or title: the record of rights, a licensed surveyor and a lawyer decide those.

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