Empty House Probability: How Common Is an Empty 7th House?
Venusward Research · Published September 13, 2026
An empty house means no planet in your chart landed inside it, purely a matter of geometry, not an omission and not a warning sign. Venusward calculated 20,000 simulated birth charts under Placidus and Whole Sign houses, using ten commonly counted planets, then measured how often the 7th house came back empty.
Key Numbers
| Metric | Value |
|---|---|
| P(7th house empty) — 10 planets, Placidus | 49.02% (±0.69%) |
| P(7th house empty) — 10 planets, Whole Sign | 49.10% (±0.69%) |
| P(7th house empty) — 12 planets, Placidus | 41.38% (±0.68%) |
| P(7th house empty) — 12 planets, Whole Sign | 40.81% (±0.68%) |
| Average empty houses per chart — Placidus | 5.723 ± 0.015 |
| Average empty houses per chart — Whole Sign | 5.672 ± 0.015 |
The ten planets counted here are the Sun through Pluto; the 12-planet count adds Chiron and the North Node. Numbers are from the "us" sample group (ten equally weighted U.S. cities) — see House System Disagreement for how often Placidus and Whole Sign reach a different verdict on the same chart.
By 7th House Cusp Sign
P(7th house empty), Placidus houses, 10 planets, same 20,000-chart run, broken out by the sign on the 7th house cusp:
| 7th house sign | n | P(empty 7th house) |
|---|---|---|
| Aries | 2,119 | 62.39% |
| Taurus | 1,987 | 56.47% |
| Gemini | 1,948 | 45.07% |
| Cancer | 1,567 | 35.61% |
| Leo | 1,228 | 25.81% |
| Virgo | 1,124 | 23.31% |
| Libra | 1,068 | 24.91% |
| Scorpio | 1,254 | 32.46% |
| Sagittarius | 1,645 | 53.98% |
| Capricorn | 1,952 | 62.30% |
| Aquarius | 2,037 | 60.43% |
| Pisces | 2,071 | 64.61% |
Method
20,000 simulated birth charts, birth dates spread uniformly from 1940 through 2005, placed across ten U.S. cities (the "us" sample group) with equal weight per city. Each chart is calculated twice: once under Placidus houses (the same production degradation function the free calculator uses, `calcHousesWithDegrade()`) and once under Whole Sign houses (`sweph.houses_ex(..., "W")`). Planet positions use the Swiss Ephemeris library in its file-free Moshier mode (`SEFLG_MOSEPH`) — the same mode the production calculator uses, measured against real ephemeris files at a maximum difference of 0.000260°, well inside the 0.01° tolerance this simulation cares about.
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 (per-sign sample sizes and confidence intervals): docs/semrush-exports/astro/kw-mining-2026-08-27/H-empty-7th-house-sim.csv.
Limits
The by-sign table samples ten specific U.S. cities, not a continuous population distribution, and covers birth years 1940–2005 only. A second run with a different random seed moved one cell (12-planet Placidus, "us" group: 41.38% on the first seed, 40.30% on the second, a 1.08-point gap) past the ±1 percentage point tolerance this simulation targets — a normal sampling fluctuation at this sample size (about 2.2 standard errors, expected to happen occasionally across eight comparisons), not a methodology defect, and it doesn't change which of the two planet-count conditions has the lower empty rate. None of this describes marriage timing, an individual chart, or an outcome — only how often a purely geometric condition occurs across a simulated sample.
How to Cite
Venusward. "Empty House Probability in Birth Charts" (2026). https://venusward.com/research/empty-houses
Planet-in-house sensitivity: Venus and Moon in the 7th and 8th (2026-09-17)
Monte Carlo simulation: 20,000 simulated birth charts per run, birth moments drawn uniformly across 1940 through 2005 UTC, spread over ten equally-weighted U.S. cities. Both house systems, Placidus and Whole Sign, are computed with the same production function the free calculator uses, `calcHousesWithDegrade()`, called once per system on each chart; planet longitudes use the same production Swiss Ephemeris call in Moshier mode. The full run was repeated with a second, independent random seed to check how much each percentage moves between samples.
Figures below are from the primary run (seed 1, n=20,000 per configuration) and are percentages. Sampling margin (95% CI) is on the order of ±0.4 percentage points for the two occupancy columns and ±1.5–2.4 percentage points for the four conditional columns (flip rate, cusp proximity, birth-time stability).
| Configuration | P(occupancy), Placidus | P(occupancy), Whole Sign | Two-system flip rate | ≤3° of nearest cusp | ≤5° of nearest cusp | ±15 min, both directions stable | ±60 min, both directions stable |
|---|---|---|---|---|---|---|---|
| Venus in the 7th house | 8.6% | 8.5% | 50.4% | 18.0% | 31.0% | 76.3% | 7.1% |
| Moon in the 7th house | 8.5% | 8.4% | 51.8% | 19.8% | 33.5% | 75.4% | 7.4% |
| Venus in the 8th house | 8.3% | 8.5% | 52.6% | 19.0% | 30.9% | 76.6% | 6.8% |
| Moon in the 8th house (control, no blog post) | 8.4% | 8.5% | 52.8% | 20.9% | 34.0% | 74.8% | 7.8% |
The two-system flip rate sits near 50% because a Placidus cusp falls at an offset from the whole-sign boundary that is close to uniformly distributed across 0–30°, so the two systems agree or disagree on occupancy in roughly equal measure. The "both directions stable" figures run lower than either single direction alone, which keeps 87–88% of occupants at ±15 minutes, because requiring both the +15-minute and -15-minute shifts to land in the same house is a stricter, joint condition. Instability comes from house cusps moving roughly 15° per hour of birth time, not from planetary motion: the Moon itself moves only about 0.55° per hour, negligible by comparison.
This run covers ten U.S. cities, not a globally representative population. The four conditional columns swing by up to about 3.8 percentage points between the two random seeds, wider than the occupancy columns, an expected consequence of the smaller sample size once conditioned on occupancy. These are geometric facts about house placement, not predictions about any relationship. Script: scripts/research/planet-in-house-sim.mjs. Full data: docs/audits/blog/planet-in-house-sim-2026-09-17.json.