State the house system before comparing the results.
NatalChart.AI calculates every chart with Placidus houses and offers no house-system switch. The Whole Sign column on this page is derived from the same demonstration chart for comparison only; the product does not display it.
The practical difference
| Question | Placidus | Whole Sign |
|---|---|---|
| How are houses defined? | A time-based division tied to diurnal motion | Each zodiac sign is one house, beginning with the rising sign |
| Are the houses equal? | Their zodiac spans vary | Each house spans one full 30-degree sign |
| Where is the Ascendant? | It marks the first cusp in a standard valid calculation | Its degree lies within the first sign-house |
| What about the Midheaven? | It marks the tenth cusp in a standard valid calculation | It remains a chart point and need not fall in the tenth house |
| What changes in a comparison? | House boundaries and possible planet-house assignments | House boundaries and possible planet-house assignments |
Whole Sign is not the same as Equal House starting at the Ascendant’s exact degree.
One birth, two sets of houses
The demonstration chart rises at 14°59′ Aquarius, with the Midheaven at 9°54′ Sagittarius. Under Placidus the cusps below come from the calculation; under Whole Sign house 1 is the whole of Aquarius and each following sign is the next house.
| House | Placidus cusp | Placidus span | Whole Sign house |
|---|---|---|---|
| 1 | 14°59′ Aquarius | 58.76° | 0° to 30° Aquarius |
| 2 | 13°45′ Aries | 34.31° | 0° to 30° Pisces |
| 3 | 18°03′ Taurus | 21.84° | 0° to 30° Aries |
| 4 | 9°54′ Gemini | 18.00° | 0° to 30° Taurus |
| 5 | 27°53′ Gemini | 19.00° | 0° to 30° Gemini |
| 6 | 16°54′ Cancer | 28.09° | 0° to 30° Cancer |
| 7 | 14°59′ Leo | 58.76° | 0° to 30° Leo |
| 8 | 13°45′ Libra | 34.31° | 0° to 30° Virgo |
| 9 | 18°03′ Scorpio | 21.84° | 0° to 30° Libra |
| 10 | 9°54′ Sagittarius | 18.00° | 0° to 30° Scorpio |
| 11 | 27°53′ Sagittarius | 19.00° | 0° to 30° Sagittarius |
| 12 | 16°54′ Capricorn | 28.09° | 0° to 30° Capricorn |
Demonstration birth: 1991-09-06 at 18:30 local time, Kyiv, Ukraine (50.4501° N, 30.5234° E), Europe/Kyiv at UTC+3, so 1991-09-06 15:30 UTC. Tropical zodiac, Placidus houses, Swiss Ephemeris 2.10.03. Full result and settings on How to verify your birth chart.
The Placidus spans are unequal: house 7 runs from 14°59′ Leo to 13°45′ Libra, 58.76° of the zodiac, while every Whole Sign house is exactly 30°. The Midheaven stays at 9°54′ Sagittarius in both; under Whole Sign it falls in house 11 rather than marking the tenth cusp.
Four bodies, both systems
| Body | Position | Placidus house | Whole Sign house | Same? |
|---|---|---|---|---|
| Sun | 13°33′ Virgo | 7 | 8 | no |
| Moon | 19°01′ Leo | 7 | 7 | yes |
| Mars | 3°28′ Libra | 7 | 9 | no |
| Saturn | 0°51′ Aquarius | 12 | 1 | no |
The positions do not move; only the boundaries do. The Sun at 13°33′ Virgo sits in Placidus house 7 because the eighth cusp is at 13°45′ Libra, but Virgo is the eighth sign from Aquarius, so Whole Sign puts it in house 8. The Moon at 19°01′ Leo lands in house 7 either way. Mars at 3°28′ Libra is still before the eighth cusp under Placidus (house 7) and in house 9 under Whole Sign. Saturn at 0°51′ Aquarius is in the rising sign, so Whole Sign gives house 1, while Placidus places it in house 12 because it lies before the first cusp at 14°59′ Aquarius.
Compare one planet at a time
Use the same birth data, coordinates, timezone and zodiac. Record each planet’s longitude, then compare its house assignment in both systems.
Do not predict the house from the planet’s degree alone. A planet at 28 degrees of a sign is not automatically in a particular Placidus house.
A useful comparison names the settings and shows the actual cusps or boundaries beside the result.
Time and location still matter
Both methods depend on establishing the rising sign or Ascendant from the birth input. Whole Sign does not remove an unknown-time problem. See how to find your birth time.
Some house calculations are limited at high latitudes. Any alternative method used after a failed calculation should be identified rather than silently labelled as the requested system.
Which result should I use here?
Read the method stated with the chart. In NatalChart.AI the stated method is always Placidus. If you compare it with another calculator, match the settings first.
The choice of house system belongs to an astrological tradition; computational consistency does not establish that one interpretation must be true.
Questions
Should the planet’s sign change when I switch only the house system?
Not if the birth input and zodiac calculation remain the same. Check for another changed setting.
Does being far from a cusp guarantee the same house in both systems?
No. Compare the actual boundaries; the systems can differ substantially.
Is matching the house system enough for a comparison?
Also match the birth data, timezone, coordinates and zodiac. Check the settings for any additional points or aspects being compared.
Next: Houses in astrology · Verify your chart · Tropical and sidereal · All calculators