Cent, Ground and Guntha Converter — which ones are exact

Two of these are fractions of an acre. One is not, and that is the whole problem. A cent is exactly one hundredth of an acre — 435.6 ft², 40.468564224 m² — and the Government of India's own Glossary of Revenue Terms says so in words, as does the Bihar revenue glossary for the same unit under its eastern name, dismil. A guntha is one fortieth of an acre, 1,089 ft², which is also exactly 121 square yards — an eleven‑yard cadastral chain squared, which is where the unit comes from. A ground is 2,400 ft², and 2,400 is not a fraction of anything: it is 18.15 grounds to the acre and 5.5096 cents to the ground. When the arithmetic comes out that ugly, you are looking at a market convention rather than a definition, and it will not survive a trip to another district.

The acre itself changed on 1 January 2023, and the conversion table you have saved may predate it. The United States kept two feet until then: the international foot at 0.3048 m exactly, and the U.S. survey foot at 1200/3937 m. NIST and NOAA retired the survey foot in a Federal Register notice, and since that date the acre is 43,560 international square feet = 4,046.8564224 m² exactly. The old survey‑foot acre was 4,046.872609874 m². The gap is about 1.6 m² on a hundred acres — nothing on a house plot, and quite enough to matter on a cadastre. Every figure on this page runs on the international foot.

The guntha caveat is in the source, not added by us. The Government of India glossary entry reads “1 Guntha = 1/40 acre, but local definition may vary.” That is the government flagging its own unit as unstable. What is worth saying next is what we did not find: no government source publishes a different numeric guntha for any particular state. The variation is asserted in the abstract and never quantified. So this page uses 1/40 of an acre, shows the caveat, and refuses to invent state‑by‑state guntha values to fill the gap — which is exactly what a calculator that wanted to look complete would do. Three independent government documents do agree on the 40‑per‑acre figure itself: the glossary, a Karnataka land‑records evaluation on the national government CDN, and an Andhra Pradesh government order that equates 25 cents with 10 guntas, which only works if an acre is both 100 cents and 40 guntas.

Ground is a Chennai convention, and it is not what your patta says. The only government use of the unit we could open is a rate line in Greater Chennai Corporation's property tax method: “Rent per 2400 Sq.feet (One Ground) = Rs. 8.00 P.M.” That is the corporation using the unit to price vacant land, not defining it. Meanwhile the Government of India glossary's Tamil Nadu chapter shows the official record of rights — patta, chitta, A‑register, town survey land register — recording extent in hectares and ares. Non‑government sources claim 2,200 ft² in some older Chennai localities; we found nothing official supporting that, so it is reported here as a claim and not offered as an option. If a document states its own area, read the document.

What this converter refuses to offer, and why that is the useful part. Ankanam is missing because the sources contradict each other — 72 ft² generally, 36 in Tirupati, 54 elsewhere — and the string “ankan” does not appear anywhere in the Government of India glossary, including the Andhra Pradesh and Telangana chapters. Kuzhi, ma, kani and veli are missing for the same reason, and even the calculator farms that publish them warn that the values differ by locality. Bigha is missing because it varies across at least eight states and nobody has reconciled it. A converter that offers a unit it cannot source is not more useful than one that says so; it is the same tool with the warning removed. If you need one of these, the answer is in the deed, the patta or the survey record, not in a conversion factor.

Where to go next. If your document is in marla or kanal, those are worse again — Punjab legally recognises four different karam lengths, so the same “5 marla” plot spans a 49% range by district, and that is handled on its own page. For plain metric and imperial area, including Korean pyeong and Japanese tsubo, the general area converter does the exact‑definition arithmetic without the regional units.