The main principle of Vedic meter is measurement by the number of syllables. The metrical unit of verse is the pada ("foot), generally of eight, eleven, or twelve syllables; these are termed gāyatrī, and jagatī respectively, after meters of the same name. A is a stanza of typically three or four padas, with a range of two to seven found in the corpus of Vedic poetry. Stanzas may mix padas of different lengths, and strophes of two or three stanzas (respectively, pragātha and ) are common.
Syllables in a pada are also classified as metrically short (laghu "light") or long (guru "heavy"): a syllable is metrically short only if it contains a short vowel and is not followed by consecutive consonants in the same pada. All other syllables are long, by quality (having a long vowel or diphthong) or by position (being followed by a consonant cluster.) Comparison with the Avestan literature shows that originally there were no constraints on permissible patterns of long and short syllables, the principle being purely quantitative. Vedic prosody innovated a number of distinctive rhythms:
There is, however, considerable freedom in relation to the strict metrical canons of Classical Sanskrit prosody, which Arnold (1905) holds to the credit of the Vedic bards:
It must be plain that as works of mechanical art the metres of the Rigveda stand high above those of modern Europe in variety of motive and in flexibility of form. They seem indeed to bear the same relation to them as the rich harmonies of classical music bear to the simple melodies of the peasant. And in proportion as modern students come to appreciate the skill displayed by the Vedic poets, they will be glad to abandon the easy but untenable theory that the variety of form employed by them is due to chance, or the purely personal bias of individuals; and to recognize instead that we find all the signs of a genuine historical development.
The principal difference between the two forms of trimeter is in the rhythm of the cadence: generally trochaic for padas and iambic for jagatī padas. Except for one significant collection, gāyatrī padas are also generally iambic in the cadence. The compatibility of iambic cadence underlies the significant variety of mixed meters combining gāyatrī and jagatī padas.
A well-known quantitative scheme in the traditional literature classifies the common meters according to the syllable count of a stanza, as multiples of 4: thus, dvipadā virāj (20), gāyatrī (24), (28), (32), (36), pańkti (40), (44), and jagatī (48). This scheme omits the original virāj entirely (with 33 syllables) and fails to account for structural variations within the same total syllable count, such as the 28 syllables of the kākubh (8+12+8) versus the (8+8+12), or the 40 of the later virāj (4x10) versus the pańkti (5x8). More comprehensive schemes in the traditional literature have been mainly terminological, each distinct type of stanza carrying its own name. The classification is exhaustive rather than analytic: every variant actually found in the received text has been named without regard to any need for metrical restoration.