What Ayadi Shadvarga actually is
Ayadi Shadvarga is the six-fold dimensional test set out in the Shilpa Shastra literature — Mayamata and Manasara are the texts most often cited, and the Tamil and Kerala sthapati lineages carry their own working versions. Its job is narrow and mechanical: once a plan is settled, Ayadi asks whether the dimensions you will build to, expressed in a traditional unit, are arithmetically well-formed. Six remainders come out, each read against a traditional list. Nothing about the site, the owner or the entrance direction enters into it — those are a different set of tests entirely.
Why perimeter, not area
Newcomers almost always expect a rule about square footage. Ayadi works on perimeter instead, and there is a reason. Area is a product of two dimensions, so it grows quadratically and two very different buildings can share it — a 40 × 15 and a 24 × 25 both give 600 sq ft, but they are not the same building. Perimeter is linear, it tracks the actual length of wall being set out with a measuring cord, and in a tradition where the cord was the instrument, the perimeter was the number you genuinely had in hand. The six remainders are therefore remainders on a quantity a mason could verify without arithmetic on a page.
What the six values signify
Aaya is gain and Vyaya is loss; they are read as a pair, and the traditional condition is simply that Aaya should be the larger. Yoni assigns the building to one of eight classes, each with an animal or emblem and a compass direction — this is the “vastu degree chart” people often go looking for, and it is reproduced in full below. Vara yields a weekday, Nakshatra one of the twenty-seven stars, usually compared with the owner’s birth star, and Tithi a lunar day, where the Rikta tithis and Amavasya are the ones commonly avoided. Of the six, Aaya, Vyaya and Yoni carry most of the weight in ordinary domestic practice; the last three are more often used to time the foundation than to reject a plan.
An arithmetic fact worth knowing before you start
Two constraints fall straight out of the multiplier set, and most online calculators never mention them. First, because 8 and 12 share a factor of 4, the Aaya remainder can only ever be 0, 4 or 8 — so the only Aaya readings that exist under this convention are 12, 8 and 4. Any advice that Aaya should come out odd is describing a different multiplier set. Second, the Yoni remainder takes the parity of the perimeter: an even perimeter in angulas always gives an even Yoni, and all four even yonis (Dhooma, Shwana, Khara, Kaka) are the ones traditionally set aside for dwellings. Since a rectangle in whole feet or whole inches always converts to a perimeter that is a multiple of 8 angulas, every such building lands on Yoni 8, Kaka. This is not a flaw in anyone’s plan — it is what happens when a system designed around the angula is fed dimensions rounded to the foot, and it is precisely why setting out is traditionally done in angulas and hasta.
A worked example
Take a built block of 28 ft 4 in × 21 ft 0 in, that is 340 in × 252 in.
Aaya 8 exceeds Vyaya 1 and the Yoni is Dhwaja, the flag — a result a practitioner would accept. Note how it was reached: not by a round 28 × 21, but by carrying four inches on the length. That is the whole craft of Ayadi in one line.