[FDArchitects]

Conversion Factors are not uniform in India .
Area units are different within the state and sometimes same unit may have different conversion factors when used in different states. For example, Bigha is used in practice in both Assam and also in some states like Delhi, Rajasthan, Haryana etc. Both the Bigha units have different conversion factors to hectares. 

Rajasthan


Shahjahani Jarib(165 feet) (Rajasthan) 
1 Bigha = 1 Jarib x 1 Jarib = 165’ x 165’ = 27225 Square Feet 
1 Bigha(Shahjahani Jarib) = 0.253 Hectare

 Gantari Jarib(132 feet) (Rajasthan) 
1 Bigha = 1 Jarib x 1 Jarib = 132’ x 132’ = 17424 Square Feet 
1 Bigha(Gantari Jarib) = 0.16 Hectare
 1 Bigha = 20 Biswansi (Rajasthan) 

Jharkhand
1 Acre = 4046.94 Sq metre (Jharkhand) 
1 Dismil = 40.46 Sq metre (Jharkhand) 
1 Katha(Jharkhand) = 66.89 Sq metre (Jharkhand) 
1 Dur = 10 Sq metre (Jharkhand) 

1 hectare = 404.68458 Acre(Tripura) 
40 Are = 1 Acre 
1 Lessa = 144 Sq feet 
1 Katha = 5 Lessa or 720 Sq feet
 
Assam
1 Bigha(Assam) = 4 Katha or 20 Lessa or 2880 Sq feet 

Kerala
2.47105 Acres = 1 Hectare (Kerala) 
1 Are = 2.47105 cents (Kerala) 
1 Acre = 100 cents (Kerala,Tamil nadu) 
1 Cent = 40 Sq metres or 435 Sq feet 

Andhra Pradesh and Karnataka
1 Acre = 40 Guntas(Andhra Pradesh and Karnataka) 
1 Gunta = 100 Sq metres (around 1100 sq feet) 
1 Acre = 121 Sq yards 
1 Kuncham = 10 cents(Andhra Pradesh) 
1 Sq link = 0.0404687 Sq metre (Kerala) 


Before Bandobust(Settlement) 
1 Karam = 57.157” (Haryana) 
1 Biswansi = 1 Karam x 1 Karam (Haryana) 
20 Biswansi = 1 Biswa (Haryana) 
1 Bigha = 20 Biswa (Haryana) 
4 Bigha-16 Biswa = 1 Acre (Haryana)
2.47 acre = 1 hectare(CG) 


Government Settlement 
1 Karam = 57.157” (Haryana) 
20 Biswansi = 1 Biswa (Haryana) 
1 Bigha = 20 Biswa (Haryana) 
4 Bigha = 1 Kila (Haryana) 
1 Kila = 40 Karam x 40 Karam (Haryana) 

After Bandobust(Settlement)
 1 Karam = 66” (Haryana) 
1 Sarsaai = 1 Karam x 1 Karam (Haryana) 
9 Sarsaai = 1 Marla (Haryana) 
20 Marla = 1 Kanal (Haryana) 
8 Kanal = 1 Acre (Ghuman) (Haryana) 
1 Acre = 36 Karam x 40 Karam (North to South, East to West) (Haryana) 
2.5 Acre = 1 Hectare (CG)


1 centi-are = 1 Sq metre 

1 centi-are = 10.76 Sq.feet 
100 Centi-are = 1 Are 
100 Are = 1 hectare 
100 Sq metre = 1 Are 
1 hectare = 100m x 100m = 10000 Sq metre 


reference: 
http://dolr.nic.in/dolr/mpr/mastercodes/...tcodes.pdf

[Manish Jain]

In Jaipur following conversion are used for land measurement. 

1 bigha  = 3024 Sq. Yards
             = 27216 Sq. Feet
             = 2528.4 Sq. Meter
             = 20 Biswa 

1 Biswa  = 151.2 Sq. Yards
             = 1360.8 Sq. Feet
             = 126.4 Sq. Meter