In a 13-sign sidereal chart, if you count the houses sign by sign starting from your rising sign, you end up with thirteen houses instead of twelve.

I want to be upfront about this: there is no agreed standard for it. What follows is how I do it in my own readings, and other astrologers may do it differently. I would rather tell you that now than have you find out later.

What a house is

Houses are the areas of life a chart is split into. In the usual twelve-house layout the first house is about self and how you meet the world, the second is about money and resources, the fourth is about home, the seventh is about partnerships and the tenth is about work and public life. The exact wording varies by author, but the idea is consistent: the sign says how a planet behaves, and the house says where that plays out.

There are several ways to divide a chart into houses. The simplest is called whole-sign houses. The first house is the entire sign that is rising on the eastern horizon at your birth moment. The second house is the next sign, and so on around the circle. With twelve signs that gives twelve houses, each exactly one sign wide. This is the method Vedic astrology commonly uses, and it is one of the oldest in the Western tradition too. Other systems, such as Placidus, cut the houses into unequal sizes.

What changes with thirteen

Ophiuchus makes the circle thirteen signs, so the whole-sign method gives thirteen houses. The thirteenth house is simply the sign just before your rising sign. In practice it is a house that does not exist in a tropical chart, so it is a new piece of ground.

Because the 13-sign zodiac uses the constellations at their real, unequal sizes, the houses are unequal in width too. A house might be only about 7 degrees wide (that is Scorpius) or about 44 degrees wide (Virgo), depending on which constellation it is. That is a strange feeling if you are used to tidy 30-degree slices, and it is also the honest consequence of following the stars literally. To see why the signs are uneven, read the 13-sign zodiac explained.

Why this is unusual

When I looked, I did not find an established standard for thirteen houses. Most 13-sign material stops at the signs and does not go on to houses. So this part is closer to a working method than to an established tradition. I use it because it keeps the chart internally consistent: the signs, the houses and the planets all follow the same constellations. If I mixed twelve equal houses with thirteen uneven signs, the chart would contradict itself.

What I do not claim

I do not claim the thirteenth house has a proven meaning. In my readings its themes come from the same notes I use for the other houses, written to fit the position, and I say plainly that this is interpretation. If a house does not fit your life, that tells you something about the method, and you are free to discard it.

I also do not claim that thirteen houses is better than twelve. For most people, twelve houses is a perfectly good way to read a chart, and there is centuries of writing to draw on. Thirteen is an experiment I find interesting and I try to label it as one.

Reading a house

Whichever system you use, a house tells you where a planet's theme shows up in your life. If Mars falls in a particular house, you would read Mars as drive and friction, and then ask where that plays out for you. A short example:

  1. Find the planet you want to read.
  2. Note its sign. This is how it behaves.
  3. Note its house. This is where it shows up.
  4. Ask whether the description fits, and keep only what does.

To see the basics, read how to read a birth chart.

A quick test of whether you like this

Try reading one planet twice: once in a twelve-house chart and once in a thirteen-house chart. If the second one says something that makes you stop and think, it did its job. If it says nothing, no harm done, and you now know which system you prefer.

See it on a real chart

The Solar Blueprint reading includes a Sidereal 13 option with thirteen houses, and shows the same chart in the other three systems too. I write every reading myself with my own engine and check it before it goes out. If you want to talk it through, come and say hello in the ADHD MindFlow community.

Astrology is a way to reflect, not science, and it does not predict events.

Astrology is a way to reflect, not science, and it does not predict events. Astronomy facts here are checked against the sources linked. Read our sources, commercial disclosure and editorial approach.