Horary fertility analysis is the specialist branch of horary astrology that judges pregnancy and conception questions. Lilly devoted a chapter to it; modern practitioners (Olivia Barclay, Deborah Houlding, Lee Lehman) refined it. The technique reads the chart for the moment a serious fertility question is asked, identifies the querent (L1), the children's significator (L5), the Moon, and the fertility-related Arabic Parts, then judges by sign fertility, applying aspects, and the perfection of the L1-to-L5 contact.
How the analysis works
The calculator casts a chart for the moment you ask the question, at your location. Then it runs five layers of testimony:
Sign fertility of the Moon, the 5th house cusp, the 5th house ruler, Jupiter, and the Ascendant. Cancer, Scorpio, Pisces are most fertile per Lilly. Gemini, Leo, Virgo are barren. The other six are semi-fruitful or neutral. Each point gets a fertility classification with a weight in the score.
Primary testimony (L1 to L5). The Lord of the 1st house represents the querent. The Lord of the 5th represents children. An applying harmonious aspect between them — sextile or trine — is the strongest yes testimony in Lilly's tradition. A square or opposition is the strongest delay or denial. No aspect at all sends the judgement to secondary perfection (translation or collection of light).
Secondary testimony (Moon to L5). When the Moon applies to the 5th house ruler, that confirms or contradicts the primary testimony. A favorable Moon-to-L5 aspect compensates for a weak L1-to-L5; an unfavorable one weakens the primary.
Arabic Parts. Part of Children (Ascendant + Saturn - Jupiter) and Part of Pregnancy (Ascendant + L5 - Moon) add independent indicators. Their sign placement, dignity, and house show additional fertility texture.
5th house analysis. The 5th house cusp sign, its ruler, the ruler's dignity, and the ruler's own sign fertility all weigh in. A dignified 5th-house ruler in a fruitful sign is a strong yes; a debilitated ruler in a barren sign points to challenges.
What the fertility score means
The score runs 0 to 100. Above 70 is favorable (clear positive testimony, multiple supporting factors). 50 to 70 is mixed (genuine indications both ways — needs human judgement). Below 50 is challenging (testimony favors delay or no). The score is a weighted aggregate, not a probability. A 65/100 chart with strong L1-to-L5 perfection still beats a 75/100 chart with no perfection.
The answer field returns one of: favorable, challenging, mixed, unclear. Use it as the headline; use the score for nuance; use the reasoning for the specific factors.
Timing windows
When the chart is favorable and the Moon has applying aspects, the calculator returns timing windows. Each window names the time unit (days, weeks, months, years), a numeric estimate, and a confidence level (low, moderate, high). Timing is derived from the degrees-to-perfection of the relevant aspect, modified by the Moon's sign type (cardinal = quick, fixed = slow, mutable = varies) and the house position of the timing planet.
Timing is not delivered when the Moon is void of course. Lilly's rule: a void Moon cannot bring a matter to perfection, and timing predictions from a void chart are unreliable. The calculator surfaces this explicitly rather than guessing.
Considerations before judgement
Before any horary judgement, Lilly required checking the chart's radicality — its fitness to be judged. The calculator runs all eight standard considerations: early Ascendant (under 3°), late Ascendant (over 27°), Moon void of course, Saturn in the 1st house (bad for the astrologer), Saturn in the 7th (bad for the question), Via Combusta on Moon or Ascendant (15° Libra to 15° Scorpio), and Ascendant ruler combust.
When considerations are present with high severity, the calculator recommends caution or decline. A radical chart with score above 80 is the strongest case for trusting the judgement.
When to use this versus the natal chart
Use the natal chart to assess a person's lifetime fertility potential, the 5th-house themes across their life, and the timing of major fertility windows via profections and transits. Use horary fertility for a specific question asked at a specific moment, with a specific answer expected within a finite timeframe.
The two are complementary. A natal chart with strong 5th-house testimony plus a favorable horary chart in the relevant window is the strongest case. A natal chart pointing to challenges plus a mixed horary suggests the question may need to be reframed (medical support, timing variants, alternative paths).
For the general horary calculator covering other question types, see the horary calculator. For the natal pregnancy-significator scan, see the natal chart feature and the profections calculator. For the broader predictive timing engine, see that feature page.