A Yojana (Sanskrit : योजन) is a Vedic measure of distance that was used in ancient India. A Yojana is about 12-15 km. (i.e. 4 Kosh = 1 Yojana and 1 kosh is 2 - 3.5 km)
In modern Hindi the word yojanaa (Hindi : योजना) means "plan" or blueprint, and is etymologically connected with the Cartesian notion of distance in the word yojana. However, note that the words "yojana'" and "yojanaa" are different, and pronounced differently. The last sound of the second word is pronounced "aaa" as in arm [ārm].
The length of the yojana varies depending on the different standards adopted by different Indian astronomers. In the Surya Siddhanta of the 5th century, for example, a yojana was equivalent to 8.0 km (5 mi), and the same was true for Aryabhata's Aryabhatteeya (499). However, 14th century scholar Paramesvara defined the yojana to be about 1.5 times larger, equivalent to about 13 km (8 mi).A. C. Bhaktivedanta Swami Prabhupada gives the equivalent length of a yojana as about 13 km (8 mi) throughout his translations of the Bhagavata Purana. Some other traditional Indian scholars give measurements between 3 km and 6 km (4–5 miles) or thereabouts. In The Ancient Geography of India, Alexander Cunningham says that a yojana is traditionally held to be between 8 and 9 miles and calculates by comparison with Chinese units of length that it could have been between 6.7 mi (10.8 km) and 8.2 mi (13.2 km).
^Vishnu Purana, Translated to English: 45:6 In the other three Puráńas, in which this legend has been found, the different kinds of inhabited places are specified and p. 46 introduced by a series of land measures. Thus the Márkańd́eya states, that 10 Paramáńus = 1 Parasúkshma; 10 Parasúkshmas = 1 Trasareńu; 10 Trasareńus = 1 particle of dust, or Mahírajas; 10 Mahírajasas = 1 Bálágra, 'hair's point;' 10 Bálágras = 1 Likhyá; 10 Likhyás= 1 Yúka; to Yúkas = 1 heart of barley (Yavodara); 10 Yavodaras = 1 grain of barley of middle size; 10 barley grains = 1 finger, or [an] inch; 6 fingers = a Pada, or foot (the breadth of it); 2 Padas = 1 Vitasti, or span; 2 spans = 1 Hasta, or cubit; 4 Hastas = a Dhanu, a Danda, or staff, or 2 Nárikás; 2000 Dhanus = a Gavyúti; 4 Gavyútis = a Yojana. The measurement of the Brahmáńd́a is less detailed. A span from the thumb to the first finger is a Pradeśa; to the middle finger, a Nála; to the third finger, a Gokerna; and to the little finger, a Vitasti, which is equal to twelve Angulas, or fingers; understanding thereby, according to the Váyu, a joint of the finger; according to other authorities, it is the breadth of the thumb at the tip. (A. R. 5. 104.) The Váyu, giving similar measurements upon the authority of Manu, although such a statement does not occur in the Manu Sanhitá, adds, that 21 fingers = 1 Ratni; 24 fingers = 1 Hasta, or cubit; 2 Ratnis = 1 Kishku; 4 Hastas = 1 Dhanu; 2000 Dhanus = l Gavyúti; and 8000 Dhanus = 1 Yojana. Durgas, or strong holds, are of four kinds; three of which are natural, from, their situation in mountains, amidst water, or in other inaccessible spots; the fourth is the artificial defences of a village (Gráma), a hamlet (Khet́aka), or a city (Pura or Nagara), which are severally half the size of the next in the series. The best kind of city is one which is about a mile long by half a mile broad, built in the form of a parallelogram, facing the northeast, and surrounded by a high wall and ditch. A hamlet should be a Yojana distant from a city: a village half a Yojana from a hamlet. The roads leading to the cardinal points from a city should be twenty Dhanus (above too feet) broad: a village road should be the same: a boundary road ten Dhanus: a royal or principal road or street should be ten Dhanus (above fifty feet) broad: a cross or branch road should be four Dhanus. Lanes and paths amongst the houses are two Dhanus in breadth: footpaths four cubits: the entrance of a house three cubits: the private entrances and paths about the mansion of still narrower dimensions. Such were the measurements adopted by the first builders of cities, according to the Puráńas specified.