Placidus vs. Whole Sign: How Often They Disagree on an Empty House
Venusward Research · Published September 13, 2026
Placidus and Whole Sign houses can reach a different verdict on whether the same house holds a planet, purely from how each system draws its cusps rather than from any difference in the planetary positions themselves. Across 20,000 simulated charts, the two systems disagreed on the 7th house in roughly one chart in four.
Key Numbers
| Disagreement pattern | Rate (10 planets, "us" group) |
|---|---|
| 7th house empty under Placidus, occupied under Whole Sign | 12.77% (±0.46%) |
| 7th house empty under Whole Sign, occupied under Placidus | 12.84% (±0.46%) |
| Either direction, combined | 25.61% (±0.60%) |
Neither a planet's zodiac sign nor its degree changes between the two systems — only which house it gets counted into near a cusp. See Empty House Probability for the overall rate at which the 7th house comes back empty under each system on its own.
Method
Same 20,000-chart simulation as Empty House Probability (birth dates spread uniformly 1940–2005, ten equally weighted U.S. cities, Swiss Ephemeris in Moshier mode). Each chart is calculated under both Placidus (`calcHousesWithDegrade()`) and Whole Sign (`sweph.houses_ex(..., "W")`) houses, using the ten selected planets (Sun through Pluto). For every chart, the script compares whether the 7th house is empty under each system and records which of the three disagreement patterns above (if any) occurred.
Script: scripts/research/empty-7th-house-sim.mjs. Reproduce with npx tsx scripts/research/empty-7th-house-sim.mjs 20000 1 write. Full source data: docs/semrush-exports/astro/kw-mining-2026-08-27/H-empty-7th-house-sim.md.
Limits
This disagreement rate is reported for the 7th house only, from the same U.S.-city, 1940–2005 sample as Empty House Probability. A breakdown by individual planet (which specific planet most often sits near the cusp that flips) would need a separate simulation and isn't part of this run. This number describes how the two house systems classify a chart, not which system is more correct — both compute identical planetary positions and differ only in where they draw house boundaries.
How to Cite
Venusward. "Placidus vs. Whole Sign House Disagreement Rate" (2026). https://venusward.com/research/house-system-disagreement