How Sagelon calculates: methodology and accuracy
Sagelon calculates personality profiles using four independent systems: Western astrology via the Swiss Ephemeris, Chinese BaZi (Four Pillars of Destiny) using the solar calendar, Pythagorean numerology, and tarot birth cards. This page describes exactly how each system is implemented, what data is required, and where our calculations have limitations.
Western astrology
All Western astrology calculations use the Swiss Ephemeris, the standard astronomical calculation library developed by Astrodienst AG. It is the same engine used by most professional astrology software, including astro.com and Astro-Seek. The library provides planetary positions accurate to fractions of arc-seconds across a span of thousands of years.
Sagelon uses the Placidus house system, which is the most widely used house system in Western astrology. We calculate positions for the Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, the North Node, Chiron, and Lilith. All 12 house cusps are computed. Major aspects (conjunctions, oppositions, trines, squares, sextiles) are identified between planets.
Birth location coordinates are resolved through OpenCage geocoding, which converts place names into the latitude and longitude required for house calculations and local sidereal time.
Required data: Birth date, birth time, and birth location for a complete chart. Without birth time, house positions and the Rising sign cannot be calculated, and the Moon's degree is approximate (the Moon moves roughly 12 degrees per day).
Limitations: Sagelon does not calculate minor asteroids, Arabic parts, or fixed stars. These are used in some branches of astrology but are not part of our standard chart output.
Chinese BaZi (Four Pillars of Destiny)
BaZi calculations use the Chinese solar calendar (the Hsia calendar), not the lunar calendar. The year boundary falls at Lichun, approximately February 4, rather than January 1 or the Lunar New Year.
From your birth date and time, Sagelon derives four pillars: the Year Pillar, Month Pillar, Day Pillar, and Hour Pillar (when birth time is provided). Each pillar consists of a Heavenly Stem and an Earthly Branch, drawn from the traditional 60-unit Sexagenary Cycle.
The Heavenly Stem of the Day Pillar is your Day Master, which represents your core self in BaZi. There are 10 possible Day Masters, corresponding to the five elements (Wood, Fire, Earth, Metal, Water) in their Yang and Yin forms.
Required data: Birth date for the Year, Month, and Day Pillars. Birth time for the Hour Pillar.
Limitations: Traditional BaZi practitioners may use different stem/branch calculation methods or luck pillar timing. Our implementation follows the standard Hsia calendar conversion. We currently calculate pillar positions and Day Master identification; luck pillar analysis and Ten Gods relationships are included in paid reports.
Pythagorean numerology
Sagelon uses Pythagorean numerology exclusively. This is the most widely used numerology system in the Western world.
Life Path number: Calculated by reducing the full birth date (month + day + year) to a single digit through repeated addition. Master numbers 11, 22, and 33 are preserved and not reduced further. The Life Path represents the broad arc of your personality and life themes.
Expression number: Your full birth name is converted using the standard Pythagorean letter-to-number table (A=1, B=2, ... I=9, J=1, K=2, and so on), then reduced to a single digit or master number. This number reflects your natural abilities and how you express yourself.
Soul Urge number: Only the vowels of your birth name are converted and reduced using the same Pythagorean table. This number describes your inner motivations and what drives you at a deeper level.
Required data: Birth date for the Life Path number. Full birth name (as it appears on the birth certificate, for traditional accuracy) for Expression and Soul Urge numbers.
Limitations: Chaldean numerology uses a different letter-to-number mapping and is considered by some practitioners to be more accurate for certain applications. Sagelon uses Pythagorean only. Name-based numbers depend on the exact name provided. For traditional accuracy, the birth certificate name should be used, though many people choose to calculate with the name they use daily.
Tarot birth cards
Tarot birth cards are calculated from your birth date using the standard method: the digits of your full birth date are summed and reduced to produce a number within the Major Arcana range (1 through 22). This produces a Personality Card and a Soul Card, which together form a pair.
Sagelon uses the 12-pair system, which is the more common variant in tarot birth card calculation. Some practitioners use a 10-pair variant that groups the cards differently. Both are legitimate approaches; we use the 12-pair system for consistency.
Required data: Birth date only. No birth time, location, or name is needed for tarot birth cards.
Limitations: Tarot birth cards are a numerological derivation from the Major Arcana. They are not a tarot reading in the traditional sense (no card spread, no shuffling, no intuitive interpretation). They identify archetypal themes associated with your birth date.
Cross-system convergence
When multiple independent systems structurally agree about a personality trait, that signal is stronger than any single system alone. This is the core idea behind Sagelon's convergence analysis.
For example, if your natal chart shows strong Fire energy, your BaZi Day Master is Yang Fire, and your Life Path number corresponds to assertive leadership, three independent systems built by different civilizations using different mathematics are pointing in the same direction. That kind of agreement is harder to dismiss than any one reading on its own.
This is pattern matching, not prediction. We are finding where independent maps agree about the terrain of your personality. We are not claiming that any of these systems are scientifically validated for predicting specific outcomes.
Read more: Our convergence research | How the convergence map works | What is convergence?
What we do not claim
Astrology, numerology, BaZi, and tarot are not scientifically validated systems for predicting life outcomes. Sagelon does not claim otherwise.
Cross-system convergence does not prove that any tradition is "correct." It shows structural agreement between independent frameworks. When four systems built on different continents in different centuries describe similar patterns, that is an interesting observation about the frameworks. It is not proof of any metaphysical claim.
No astrology, numerology, BaZi, or tarot system should replace professional medical, psychological, or financial advice. These tools are for self-reflection and personal exploration.
Data and privacy
Birth data you enter is used for calculation. Free tools on Sagelon do not require an account. You can generate a free Convergence Snapshot or use any of our individual calculators without signing up or providing an email address.
For full details on how we handle your data, see our privacy policy.
Last updated: March 2026
Frequently Asked Questions
Does Sagelon use the Swiss Ephemeris?
Yes. All Western astrology calculations on Sagelon — Sun, Moon, Rising sign, planetary positions, house cusps, and aspects — are computed using the Swiss Ephemeris, the same astronomical library used by Astro-Seek and astro.com (Astrodienst). Planetary positions are accurate to fractions of arc-seconds.
How accurate are Sagelon's birth chart calculations?
Planetary positions are accurate to arc-seconds using the Swiss Ephemeris. House positions and the Rising sign require an accurate birth time and location. Without birth time, house positions and the exact Moon degree are approximate. Geocoding for birth locations uses OpenCage. The calculations are as precise as the birth data you provide.
What numerology system does Sagelon use?
Sagelon uses Pythagorean numerology exclusively. Life Path numbers are calculated by reducing the full birth date (month + day + year) to a single digit, preserving master numbers 11, 22, and 33. Expression and Soul Urge numbers use the standard Pythagorean letter-to-number table. We do not use the Chaldean system.
Does Sagelon predict the future?
No. Sagelon maps personality patterns using four independent systems. It identifies where those systems structurally agree about personality traits. It does not predict events, outcomes, or timing. These systems are not scientifically validated for prediction, and Sagelon does not claim otherwise.
What is cross-system convergence?
When astrology, numerology, BaZi, and tarot independently describe similar personality traits for the same person, that structural agreement is called convergence. Each system uses different mathematics and was developed by a different civilization. When they point to the same pattern, the signal is stronger than any single system alone. This is pattern recognition, not prediction.