Methods
How We Calculate
Nymelia calculates planet positions with the open source astronomy-engine library in the tropical zodiac, uses Placidus houses, converts birth times with the IANA time zone database and reduces numerology numbers with the Pythagorean table, keeping 11, 22 and 33. Our results match Swiss Ephemeris within 19 arcseconds (about 0.005 degrees).
Every result on Nymelia is calculated before any text is written. This page lists the library, the conventions and the limits behind our numbers, so you can compare them with any other source.
Our rules at a glance
Where traditions disagree, we pick one rule and state it. This table lists every rule behind our calculators, the value we use and where it comes from. The sections below explain each one.
| Rule | Value we use | Where it comes from |
|---|---|---|
| Planet positions | astronomy-engine, apparent geocentric positions | Open source library by Don Cross, MIT license; stated accuracy within 1 arcminute of NOVAS |
| Zodiac | Tropical, measured from the true equinox of date | Standard in Western astrology |
| Houses | Placidus; Whole Sign above the polar circles | A widely used system in modern Western astrology |
| Lunar node | Mean node | Formula by the astronomer Jean Meeus; checked against Swiss Ephemeris |
| Unknown birth time | Chart for 12:00 noon, no houses, Ascendant or midheaven | Our convention, flagged on every result |
| Time zones | IANA time zone database with historical daylight saving rules | Maintained by IANA, the body that also manages internet addresses |
| Birthplaces | Bundled city list with coordinates and time zone | GeoNames data, CC BY 4.0 |
| Letter values | Pythagorean table, A = 1 to I = 9, then again | Numerology convention |
| Life path | Month, day and year reduced separately, then added | Widely taught convention; the flat digit sum gives a different number on 13.9% of dates from 1940 to 2009 |
| Master numbers | 11, 22 and 33 kept | Numerology convention |
| Personal angel number | Life path repeated (7 becomes 777, 11 becomes 1111) | A popular convention, no official method |
| Synastry orbs | Conjunction and opposition 8, trine 7, square 6, sextile 4 degrees, plus 1 with Sun or Moon | Common orbs in modern practice; our choice |
| Compatibility scores | None | No traditional method produces a percentage |
Planetary positions
We calculate the positions of the Sun, Moon and planets with astronomy-engine, an open source astronomy library by Don Cross, released under the MIT license.
Positions are apparent geocentric positions: where each body appeared from the center of the Earth at your birth moment, corrected for the time light takes to travel and for aberration. They are expressed in the tropical zodiac, measured from the true equinox of date, which is the standard in Western astrology.
How we checked our accuracy
We compared our results with Swiss Ephemeris output published by Astrodienst for 7 reference charts, spread across both hemispheres and including one location above the polar circle. Planets and the mean node matched within 19 arcseconds (about 0.005 degrees), and the Ascendant and midheaven within 1 arcsecond. That is well under one arcminute, far too small to change a sign, a house or an aspect in practice.
These reference cases are part of our automated tests, so every change to the code is checked against them again.
Birth time, time zones and places
Your local birth time is converted to universal time with the IANA time zone database, which includes historical daylight saving rules. That matters more than people expect: war time in the 1940s, states that skipped daylight saving time and changing start dates can all shift a birth time by an hour.
If you enter a time that did not exist because clocks sprang forward, or a time that happened twice because clocks fell back, we point this out.
Birthplaces come from a bundled list of cities based on GeoNames data (CC BY 4.0), with coordinates and time zone for each place.
When the birth time is unknown
If you do not know your birth time, we calculate the chart for 12:00 noon local time. We then leave out the houses, the Ascendant and the midheaven, because they depend on the exact time. The Moon moves about 13 degrees a day, so it can change sign during your birth day. When that happens, we tell you that your Moon sign is uncertain.
Houses, Ascendant and lunar nodes
We use the Placidus house system, the most common choice in modern Western astrology. Above the polar circles Placidus cannot be calculated for part of the zodiac, so for births there we switch to Whole Sign houses and say so on the result.
The Ascendant and midheaven come from the local sidereal time and the true obliquity of the ecliptic. For the lunar nodes we use the mean node. The south node is always exactly opposite the north node.
Numerology conventions
We use the Pythagorean letter table: A, J and S are 1, B, K and T are 2, and so on up to I and R as 9. Accents are removed before counting. The letter Y counts as a vowel when it is not next to another vowel, as in Lynn or Mary, and as a consonant when it is, as in Maya.
Master numbers 11, 22 and 33 are kept and not reduced further.
For the life path we reduce the month, the day and the year separately, then add them and reduce the sum. Adding all digits of the date in one go can give a different result. For example, April 29, 1969 gives 22 with our method and 4 with a flat digit sum. Both methods are in use; we chose the one that is widely taught in Pythagorean numerology and we show every step. When the other method gives a master number (11, 22 or 33) and ours does not, the result shows it as your hidden master number, because many visitors have been told that number before.
Expression uses all letters of your full birth name, soul urge uses the vowels and personality uses the consonants. Each part of the name is reduced on its own before the parts are added.
Some texts on this site mention karmic debt numbers (13, 14, 16 and 19) as part of the tradition. We do not calculate them.
Your angel number
Our angel number calculator follows a popular numerology convention, not an astronomical rule: we take your life path and repeat it. A life path of 7 becomes 777. Master numbers become four digits, so 11 becomes 1111, 22 becomes 2222 and 33 becomes 3333.
Numbers and signs compared: our theme table
The personal reading has a section on where your numbers and your chart agree and where they pull apart. Numerology and astrology are separate traditions, so to compare them we give each number and each sign one main theme, taken from the keywords the tradition attaches to it. This table is our own convention, not a classical rule. Agreement means a theme appears in your numbers (life path, expression, soul urge) and in your Sun, Moon or rising sign. A pull means one side shows a theme and the other its opposite: independence and partnership, structure and freedom, expression and depth, achievement and compassion, care and freedom.
| Theme | Numbers | Signs |
|---|---|---|
| Independence | 1 | Aries |
| Partnership | 2 | Libra |
| Expression | 3 | Gemini, Leo |
| Structure | 4, 22 | Taurus, Virgo |
| Freedom | 5 | Sagittarius, Aquarius |
| Care | 6, 33 | Cancer |
| Depth | 7, 11 | Scorpio |
| Achievement | 8 | Capricorn |
| Compassion | 9 | Pisces |
Synastry: comparing two charts
For relationship charts we look for the five major aspects between the planets of two people, with these maximum orbs: conjunction 8 degrees, opposition 8, trine 7, square 6 and sextile 4. When the Sun or Moon is involved, the orb grows by 1 degree. The Ascendants are included only when both birth times are known.
Each aspect gets a weight: personal points (Sun, Moon, Venus, Mars, Ascendant) count most, Mercury a bit less, Jupiter and Saturn less again, and the slow outer planets least, because they describe a generation more than a person. Tighter aspects count more. From these weights we show three simple indicators: harmony, tension and intensity. They describe the pattern of contacts, not the quality of a relationship.
Compatibility calculators
Zodiac compatibility compares two Sun signs by element, by mode and by their distance around the zodiac, counted the short way: same sign, semi-sextile (one sign apart), sextile (two), square (three), trine (four), quincunx (five) and opposition (six). Fire with air and earth with water count as supportive elements. We do not print percentages, because no traditional method produces them.
Numerology compatibility compares two life path numbers with one stated rule from classic numerology: odd numbers are read as active, even numbers as receptive. Master numbers count by their base digit for this comparison (11 as 2, 22 as 4, 33 as 6). Birth chart compatibility uses the same charts, orbs and weights as the synastry chart and adds a sign-by-sign table for Sun, Moon, Mercury, Venus, Mars and rising sign.
The sign pair pages add one figure from our own chart engine: how often two people with those Sun signs have Venus signs at an easy angle (same sign, sextile or trine). Venus never moves more than two signs away from the Sun, so a Sun sign allows only five Venus signs. We counted the Venus sign for every day from 1946 to 2009, 64 years or eight full Venus cycles, and combined the two Sun signs as if both people were born on random days in that span. That is a frequency, not a compatibility score: it says how common a pairing is, not how well a couple will do.
Venus sign, north node and Saturn return from a birth date
For calculators that only ask for a birth date, we compute the position at 12:00 UTC and check the whole calendar day in every time zone, from UTC+14 to UTC-12. If the planet or node changed signs within that span, the result names both signs and the moment of the change, found by bisection to well under a minute, and asks for birth time and place.
Saturn returns are found by scanning transiting Saturn in four-day steps from age 20 and refining every crossing of the natal Saturn longitude to the minute. One return can have one or three exact passes, because Saturn turns retrograde. We also give the period transiting Saturn spends in your natal Saturn sign. Natal Saturn is taken at noon UTC, which moves the dates by a day at most.
Astrocartography
Our astrocartography map shows four lines for each planet: where it was rising (AC), culminating (MC), setting (DC) and at its lowest point (IC) at your birth moment. The lines are calculated in mundo, from each planet's right ascension and declination. For each line we list larger cities within about 190 miles (300 km) east or west of it.
Vedic chart and Destiny Matrix
All Western calculators use the tropical zodiac. The Vedic birth chart is the one exception: it subtracts the Lahiri ayanamsa (23.857 degrees at January 1, 2000, growing by 50.29 arc seconds a year, within about 0.01 degrees of published tables from 1900 to 2100), counts houses whole sign from the sidereal Lagna, uses the mean lunar node for Rahu and Ketu, and dates the Vimshottari periods in years of 365.25 days.
The Destiny Matrix follows the common public version of Natalia Ladini's 2006 method: every point is a number from 1 to 22, and a sum above 22 is replaced by its digit sum. We checked it against a worked example published by another calculator (August 26, 2002 gives 8, 8, 4, 20 and 4 in the center). The chart drawing and every interpretation on this site are our own.
How readings are written
Readings follow one rule: compute, then write. First every number and position is calculated. Then the text is assembled from interpretation passages for each number, sign, house, aspect and line, drafted with AI assistance and edited by us.
An optional AI step can rewrite the assembled text so it reads smoothly. It receives only the calculated values and the edited passages, and it is instructed not to add, remove or change any position or number. Without that step, you get the edited passages directly.
What our numbers mean
The calculations are astronomy and arithmetic, and we take care to get them right. The interpretations are tradition. We offer them for entertainment and self-reflection, not as predictions or advice. Our entertainment notice spells this out.
Sources we checked
We cite only what we have read in the original. Each source below was opened and checked on October 12, 2026.
Constellation figures on the horoscope pages: d3-celestial by Olaf Frohn, data/constellations.lines.json, version 0.7.35, BSD 3-Clause License, Copyright (c) 2015 Olaf Frohn: github.com/ofrohn/d3-celestial.
- astronomy-engine by Don Cross, MIT license. Project page: github.com/cosinekitty/astronomy. States accuracy within 1 arcminute of NOVAS and tests against NOVAS and JPL Horizons.
- Swiss Ephemeris by Astrodienst (Dieter Koch and Alois Treindl), based on NASA JPL ephemerides. Information page: astro.com/swisseph. Our reference values come from Swiss Ephemeris 2.10.03 output on astro.com.
- IANA time zone database: iana.org/time-zones. It holds the history of local time for representative places worldwide.
- GeoNames geographical database, Creative Commons Attribution 4.0 license: geonames.org.
- NASA Saturn fact sheet, tropical orbit period of 10,746.94 days: nssdc.gsfc.nasa.gov/planetary/factsheet/saturnfact.html.
- Doreen Virtue, Angel Numbers 101 (Hay House, 2008), as listed in the Wikipedia article on Doreen Virtue, which also notes that she renounced her New Age beliefs in 2017.