Whole Sign vs Placidus: compare your houses

Worked example: a fictional chart

This is Lunara’s invented sample chart, not your chart or a real person’s: 1 January 1990, 12:00, London, the same fictional chart used in the empty house calculator and the sample reading. Calculated once with the method below.

The Ascendant here is at about 25° Aries, so the Whole Sign 1st house is all of Aries, from 0°. Take Mars: it stays at about 10° Sagittarius in both systems, but Placidus counts it in the 8th house and Whole Sign in the 9th. Nothing about the planet moved; the house boundary did.

How each system draws the twelve houses

Placidus divides the sky by time: it splits the arcs that points travel above and below the horizon over the day. Its cusps can fall at any degree of a sign, and houses come out different sizes, especially away from the equator. The 1st house cusp is the Ascendant degree and the 10th house cusp is the Midheaven.

Whole Sign gives each house one entire sign. The 1st house is the whole sign your Ascendant is in, from 0° of that sign, even though the Ascendant itself may be at 24°. The next sign is the 2nd house, and so on round the zodiac. That is not the same as Equal House, which measures 30° steps from the Ascendant’s exact degree. In Whole Sign the Midheaven is still a point in the chart; it often falls in the 10th house but can land in the 9th or 11th.

Why a planet can change house

When a Placidus cusp falls partway through a sign, the part of that sign before the cusp belongs to one Placidus house and the rest to the next. In Whole Sign the whole sign is one house. So a planet sitting before a Placidus cusp can be counted one house earlier in Placidus than in Whole Sign, or the other way round. Its sign and degree haven’t moved.

This comparison doesn’t pick a winner. Whole Sign is associated with older Hellenistic practice and is popular again; Placidus is the default on many modern Western chart sites, including Lunara’s. No calculation can show which system is true for you, and choosing the one whose reading you like better isn’t a test of either.

You need a recorded birth time

Both systems start from the Ascendant, which moves through a whole sign in roughly two hours and through about one degree every four minutes. A guessed or rounded time can move every house. That’s why this tool asks for a time from a record and won’t use noon or midnight instead.

If your recorded time falls in an hour that a clock change skipped or repeated, the form can’t tell which moment you mean, so it won’t calculate it. Our guide to daylight saving time and your birth chart explains what to check.

Frequently asked questions

Which house system is correct?

Neither is proven correct. They are different conventions within astrology. This tool shows both from the same chart so you can see exactly what changes; it doesn’t rank them.

Do my planet signs change between Whole Sign and Placidus?

No. Every planet keeps the same sign and degree, and the Ascendant and Midheaven stay the same. Only the house each planet is counted in can change.

Is Whole Sign the same as Equal House?

No. Whole Sign starts the 1st house at 0° of the Ascendant’s sign. Equal House starts it at the Ascendant’s exact degree and adds 30° for each house.

Which system does the paid Lunara reading use?

Placidus. The optional automated natal reading is written from Lunara’s Placidus chart. It isn’t a Whole Sign reading or a combined reading of both systems.

Why doesn’t it work for places near the poles?

Placidus can’t be calculated reliably at latitudes of 66° or more, so this comparison isn’t available there. The tool won’t quietly swap in another system.