Equal house system
The equal house system divides the chart into twelve houses of 30 degrees each, starting from the exact degree of the Lagna rather than from the sign boundary.
What it is
Its houses begin at the Lagna degree, so house 1 starts at the ascendant and each following house starts 30 degrees later. A planet close to a house cusp can fall in a different house from the one it has in whole-sign houses.
How it is worked out or read
Take the sidereal Lagna longitude as the cusp of house 1, add 30 degrees for each following house, and place each planet by its longitude. The method is simple but gives a different result from whole-sign for planets near the Lagna's own degree.
Where it appears on this site
This site does not use the equal house system in its charts. It is listed here so that you can recognise it when another calculator shows it.
A worked example
Take a Lagna at 15 degrees of Simha. In the equal house system, house 1 runs from 15 degrees Simha to 15 degrees Kanya, house 2 from 15 degrees Kanya to 15 degrees Tula, and so on. A planet at 20 degrees Simha is in house 1 in this system, but in house 1 also in whole-sign terms, since Simha is the Lagna sign. A planet at 10 degrees Kanya is in house 1 in the equal system, because it falls before the 15 degree cusp of house 2, while in whole-sign houses it is in house 2. The two systems agree on most planets and disagree on those near the Lagna's own degree.
Where the system is used
Equal house divisions are used in several traditions and in some software, sometimes because a user wants houses that begin at the exact Lagna degree. The system is simple to compute and makes the Lagna the centre of its house. Readers who meet an equal-house chart should check which system the source uses before comparing. This site does not produce equal-house charts; it is described here so that a reader can recognise the method when another calculator reports it.
Two forms of equal houses
Equal house systems divide the zodiac into twelve houses of 30 degrees each, measured from the Lagna's exact degree. In the form common in Western astrology, the Lagna degree is the start of the first house. In a form used in some Indian bhava chalit charts, the Lagna degree is the middle of the first house, which then runs from 15 degrees before the Lagna to 15 degrees after it.
Compared with whole-sign houses
This site uses whole-sign houses, in which the entire Lagna sign is the first house. Under equal houses, a planet early in the Lagna sign may fall in the twelfth house instead, and a planet late in a sign may move into the next house. Readers comparing charts should note which system each uses before treating a change in house as meaningful.