Compare Astrology House Systems Side by Side

You can pick any house system you want, and the same chart will give you different houses. Same Mercury. Same minute of birth. Different story. Most other comparison pages tell you about the difference. This one shows it across all eight major systems at once. Enter your birth data above, see your planets land in eight different systems, and notice exactly where the disagreement happens.

How your planets move between house systems

If your planets all stayed in the same houses no matter which system you picked, this calculator would not be interesting. They do not. The further a planet sits from the middle of a sign, the more likely it is to jump houses when you switch. A planet at 15° of a sign almost always agrees across systems. A planet at 28° often disagrees. The eight systems break down into four families, each carrying its own logic for where house boundaries fall.

What is the difference between Placidus and Whole Sign houses?

Whole Sign assigns each zodiac sign as a complete 30° house starting from the ascendant's sign. Placidus divides the sky by time, producing unequal houses anchored to the exact ascendant degree and the midheaven. The two systems can place the same planet in different houses, especially planets near sign boundaries.

That is the textbook answer. The longer one matters more.

How Whole Sign houses work

Find your ascendant. Whatever sign your ascendant is in becomes the entire 1st house, from 0° to 29°59'. The next sign is the entire 2nd. The next is the 3rd. Around the wheel. Every house is exactly 30° wide. Every house starts at 0° of a sign and ends at 29°59' of the same sign.

Whole Sign is the oldest documented system. Hellenistic astrologers used it as the default from roughly the 1st century BCE forward. It fell out of fashion in the Renaissance, came back in the 1990s when Project Hindsight translated the original Greek source texts, and is now the default for traditional and Hellenistic practice.

How Placidus houses work

Pick the exact degree of your ascendant, say 14°23' Cancer. That is the cusp of your 1st house. Pick the exact degree of your midheaven, say 27°08' Pisces. That is the cusp of your 10th house. Placidus splits the time it takes the sun to travel between those two angles into thirds, then maps those thirds back to the ecliptic. The result: twelve houses of unequal sizes, anchored to four exact degrees instead of four sign boundaries.

Placidus came out of the 17th century and became the default system for most modern astrology software, including the chart engine your favorite app probably uses.

The eight house systems Augurine compares

The calculator runs your chart through all eight systems in parallel. They cluster into four families: sign-based, equal, quadrant, and spatial.

Whole Sign (sign equals house)

Each sign is one house. Houses are 30° wide and anchored to the sign of the ascendant. Survives a fuzzy birth time better than any other system. Best for traditional, Hellenistic, and time-lord work.

Equal House (30° from exact ascendant)

Anchor to the exact ascendant degree. Add 30° for each successive cusp. Twelve houses, all 30° wide, with cusps mid-sign rather than at sign boundaries. Stable at high latitudes.

Placidus (time-based)

The default in most modern software. Houses are unequal and anchor to your exact ascendant and midheaven degrees. Latitudes above about 66.5° start to break, at which point Augurine falls back to Whole Sign. Best for psychological, modern, and event-timing astrology.

Porphyry (trisected quadrants)

Take the four angles. Split each of the four resulting arcs into three equal pieces along the ecliptic. Done. Named after the 3rd-century neo-Platonist; the simplest quadrant-based system, mathematically clean, stable at all latitudes including polar.

Koch (Houses of Birth)

Walter Koch's 1971 method. Starts from the birth Midheaven degree, works backward to when that degree was rising, then takes the ascendants at the intermediate thirds. Popular in German-speaking astrology and in 20th-century evolutionary practice.

Alcabitius (medieval Arabic)

A 10th-century Arabic system that trisects the ascendant's semi-arcs and projects via the meridian. It is related to Koch but not the same calculation; the two often sit close at ordinary latitudes and can still disagree on intermediate cusps.

Regiomontanus (great circles through equator)

Divides the celestial equator into twelve equal arcs from the east point and projects them onto the ecliptic via great circles passing through the north and south points of the horizon. Was the European standard before Placidus took over in the 17th century. Still used in classical horary work.

Campanus (great circles through prime vertical)

Divides the prime vertical (a great circle running east to west through the zenith and nadir) into twelve equal arcs, then maps them to the ecliptic. Geometrically clean in 3D space. Used by some practitioners working in horary and mundane astrology.

Which house system should you use?

Our position is direct. Whole Sign for traditional work, Placidus for modern. The other six are specialist tools you reach for when the question warrants them. Both default systems ship in every Augurine chart, and now all eight are computable here.

Hellenistic, traditional, or profection work, use Whole Sign

Profections, zodiacal releasing, sect, and most Hellenistic timing techniques were designed against Whole Sign. They work best, often only, when you use it. See the profection year hub for the year-by-year reading every Whole Sign chart unlocks.

Modern, psychological, or evolutionary work, Placidus or Koch

Modern astrology was built on Placidus. Liz Greene's psychological work writes in Placidus. The Magi Society writes in Placidus. Stephen Arroyo wrote in Placidus. Walter Koch's school prefers Koch. Either system fits the modern reading style.

Classical horary, use Regiomontanus

William Lilly, the most cited classical horary astrologer, worked in Regiomontanus. Modern horary practice that follows Lilly's tradition (and the Renaissance Italian school) keeps Regio as the default.

Born above 60° latitude, avoid Placidus, Koch, and Alcabitius

All three time-based systems start to distort badly that far north or south. A planet near the polar circle can land in an “impossible” house, or two cusps can collapse onto the same degree. Use Whole Sign, Equal, Porphyry, Regiomontanus, or Campanus instead. The math behaves.

Birth time is fuzzy or rectified, start with Whole Sign

Whole Sign is forgiving. A 10-minute error in your birth time rarely changes which sign rises, so your houses do not shift. Time-based systems move cusps roughly 1° every 4 minutes of birth time. If you have had your time rectified or you are working from “around 3pm,” start with Whole Sign and switch later if the chart asks for it. Run the birth time rectification tool if your time is genuinely uncertain.

Cusp planets, the biggest source of disagreement

Take a chart with the ascendant at 5° Gemini and Mercury at 28° Cancer. Mercury is a cusp planet. It is nearly out of Cancer.

In Whole Sign, Mercury is in the 2nd house. Cancer is the 2nd sign from Gemini. The whole sign is the whole house. Mercury rules Gemini, so the chart ruler sits in your house of money, resources, and what you build value around. The reading: your income, your stability, and your relationship to having tend to come through how you communicate, write, talk, and exchange.

In Placidus, Koch, Regiomontanus, and Campanus, the 3rd cusp depends on latitude, but for moderate northern latitudes with this configuration it commonly falls in the mid-20s of Cancer. Mercury at 28° has crossed it. The chart ruler now sits in the 3rd house: communication, siblings, immediate environment. The reading: your mind, your daily speech, the way you process the world around you. Money becomes a different conversation.

Same planet. Same minute of birth. Different stories. Both can be true at the same time. The point of this calculator is to put all eight readings on screen so you can decide which one your life looks more like.

Which techniques depend on your house system?

Some chart techniques are house-system-agnostic. Others fall apart if you pick the wrong one. The short list:

• Profections require Whole Sign. The profected year technique advances one whole sign per year of life starting from the rising sign. It does not work in Placidus or any quadrant system. See the profection year hub.
• Zodiacal releasing, the Hellenistic time-lord technique from Vettius Valens, is Whole Sign-native.
• Classical horary (Lilly tradition) uses Regiomontanus. Modern horary practitioners often default to Placidus or Whole Sign.
• Transits to your angles (ascendant, IC, descendant, MC) are system-independent. The angles are degrees, not houses.
• Transits to house cusps are system-dependent. A Placidus 5th cusp transit and a Whole Sign 5th cusp transit can happen years apart.
• Solar arc directions are system-independent. They move planets, not houses.
• Saturn return interpretation by house is system-dependent. See the Saturn return calculator.
• Almuten Figuris, chart ruler analysis, and Lot of Fortune calculations work in any system but are usually computed in Whole Sign for traditional readings.