How this calculation works
This page specifies Gunter’s chain as 66 international feet with 100 links. Convert each component measurement before multiplying perpendicular sides. Excess links are carried into whole chains rather than read as a decimal suffix.
Feet = (100 × chains + links) × 0.66; rectangle area = length × widthA worked example
4 chains plus 25 links = 4.25 chains = 280.5 ft = 85.4964 m. A rectangle with that length and width 2 chains plus 50 links has 46,282.5 sq ft, or 1.0625 acres.
Good to know
Gunter’s chain using the international foot only. A metric chain, another historical chain or the former U.S. survey foot needs its own definition. Rectangle area assumes horizontal perpendicular sides; old record notation and boundary validity are not inferred.
Reference: NIST: exact international-foot and acre factors (opens in a new tab) ↗
Check the land-unit definitions and sources
The standard factors use the international foot and an acre of 43,560 sq ft. Cent means 1/100 acre; gunta means 1/40 acre; the selected Chennai ground means 2,400 sq ft.
The Assam report defines bigha as 14,400 sq ft, katha as 2,880 sq ft and lecha as 144 sq ft. The cited West Bengal court order mentions a 720-sq-ft katha convention. These are explicit presets, not an automatic definition for every record or every place using the same name. Match your record to the stated convention, or use its verified custom factor.
- NIST: exact international-foot and acre factors (opens in a new tab) ↗
- API Setu MDDS: acre/cent and acre/gunta relationships (opens in a new tab) ↗
- Greater Chennai Corporation: one ground is 2,400 sq ft (opens in a new tab) ↗
- Government of Assam AIRBMP framework: section 7.2, page 28 (bigha, katha and lecha) (opens in a new tab) ↗
- Supreme Court order, 7 May 2025: paragraph 2, page 2 (West Bengal katha) (opens in a new tab) ↗
The acre relationships are converted using exact base factors. Rounded or unrelated regional values in a reference table are not substituted for these definitions.
Specify which chain the old measurement uses
The word chain does not by itself identify every historical or metric surveying instrument. This calculator uses the stated Gunter’s chain of 66 international feet, divided into 100 links. Its metre equivalent is 20.1168, with a link equal to 0.201168 m.
Four chains plus twenty-five links is 4 + 25/100 = 4.25 chains. It is not 4.25 feet. The primary result is therefore 280.5 ft, while the normalized component output keeps the original chain-and-link meaning visible.
The NIST reference distinguishes international-foot equivalents from the former U.S. survey-foot equivalents. This page uses the international-foot column. If an actual old record uses another definition, verify that definition before applying any modern metric conversion.
An acre is an area, not a required plot shape
A rectangle ten chains long and one chain wide contains ten square chains. Since 66 × 66 = 4,356 square feet, ten square chains contain 43,560 square feet, or one acre. The same area can have many other shapes and boundary lengths.
Rectangle mode first converts both entered chain-plus-link lengths, then multiplies them. A 4.25-chain by 2.5-chain rectangle has 10.625 square chains, or 1.0625 acres. Multiplying only the whole-chain components would omit both link remainders.
Measured plot area handles a different situation: modern side lengths, including three-side triangles and a four-side plot with its measured internal diagonal. Do not multiply two unrelated boundary lengths and assume the plot is rectangular.
A few questions, answered
What if I enter 125 extra links?
The tool carries them: one chain and 125 links normalizes to two chains and 25 links.
Can I use a 20-metre metric chain?
No. This page explicitly uses the 66-foot Gunter’s chain. A different chain requires a different definition, not a different spelling of the same input.
Does the rectangle option allow a sloping field?
It calculates horizontal rectangular plan area. Slope distances or non-right-angle boundaries require other measurements.