A vitasti (Sanskrit: वितस्ति, vitasti) is an ancient Indian unit of length approximating to 21 centimeters.^{[citation needed]}

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The Sanskrit word vitasti, meaning "span", is an ancient Indo-Iranian term. It is derived from the Proto-Indo-Iranian term *witasti- and is related to Avestan vītasti, Kurdish bist and Persian bidast, all meaning "span".^[1]

According to the Vāstuśāstra, a vitasti is equal to 12 aṅgulas. It is defined as the long span between the extended thumb and the little finger or as the distance between the wrist and the fingertips.^[2]

8 Paramāṇu = 1 Rathadhūli (chariot-dust)
8 Rathadhūli = 1 Vālāgra (hair-end)
8 Vālāgra = 1 Likṣā (nit)
8 Likṣā = 1 Yūkā (louse)
8 Yūkā = 1 Yava (barley)
8 Yava = 1 Aṅgula (finger)
12 Aṅgula = 1 Vitasti (span)
2 Vitasti = 1 Kiṣku (cubit)^{[citation needed]}