A Yojana (Sanskrit : योजन ) is a Vedic measure of distance that was used in ancient India. It is equivalent to about 1.6 km (1 mi) as per modern measures of distance, although the exact value is disputed among scholars (between 2 and 5 km (1 and 3 mi)) and many Vedic scholars believe that 1 Yojana equals 9.09 miles ad per Vishnu Purana CH-6 Book-1
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].
Yojana as per "Vishnu Purana"
Yojana is defined in Chapter 6 of Book 1 of the ancient vedic text “Vishnu Purana” as follows:-
10 ParamAnus equal to 1 Parasúkshma,--ParamAnu refers to atom meaning Ancient Indians knew the size of an atom
10 Parasúkshmas equal to 1 Trasarenu,
10 Trasarenus equal to 1 Mahírajas (particle of dust),--Ancient Indian knew the size of particle of dust
10 Mahírajas equal to 1 Bálágra (hair’s point),--Ancient Indians knew the size of hair's point
10 Bálágra equal to 1 Likhsha,
10 Likhsha equal to 1 Yuka,
10 Yukas equal to 1 Yavodara (heart of barley),
10 Yavodaras equal to 1 Yava (barley grain of middle size),
10 Yava = 1 Angula (1.89 cm or approx 3/4 inch)(here angula doesn't mean 1 inch rather 3/4 inch),
6 fingers equals 1 Pada (the breadth of it),
2 Padas equals 1 Vitasti (span),
2 Vitasti equals 1 Hasta (cubit),
4 Hastas equals a Dhanu,
1 Danda, or paurusa (a man’s height),
or 2 Nárikás equals 6 feet,
2000 Dhanus equals 1 Gavyuti (distance to which a cow’s call or lowing can be heard) = 12000 feet—Ancient Indian had advanced knowledge in biological sciences
4 Gavyutis equals 1 Yojana
1 Yojana equals 9.09 miles (or) 14.62894 kilometers
Variations on length
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).
- Hindu cosmology
- History of measurement systems in India
- Hindu units of time
- List of numbers in Hindu scriptures
- Vishnu purana(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 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.
- Richard Thompson (1997), "Planetary Diameters in the Surya-Siddhanta", Journal of Scientific Exploration, 11 (2): 193–200 
- O'Connor, John J.; Robertson, Edmund F., "Aryabhata I", MacTutor History of Mathematics archive, University of St Andrews.
- Srimad Bhagavatam 10.57.18 (translation) "one yojana measures about eight miles"
- Alexander Cunningham, Measures of Distance. Yojana, Li, Krosa. in The Ancient Geography of India: I. I. The Buddhist Period, Including the Campaigns of Alexander, and the Travels of Hwen-Thsang, Trübner and Company, 1871, pp. 571-574