How we calculate

Numerology

Reduction and master numbers

To reduce a number, add its digits until one digit remains: 1990 becomes 19, then 10, then 1. We stop early at 11, 22 and 33, the master numbers, because most modern numerologists treat them as distinct. The personal year and the birthday reading reduce all the way, except that birthdays on the 11th, 22nd and 29th are read as 11 and 22, as is common.

Life path

We reduce the month, the day and the year separately (keeping master numbers), add the three, and reduce the total. This component method is the one most numerology references teach. The alternative, adding every digit of the date in one sum, usually gives the same answer but can hide or create a master number. When the two methods disagree for your date, the calculator tells you and shows both.

Name numbers

We use the Pythagorean letter values, the standard system in English-language numerology:

Each part of the name is added and reduced on its own, then the parts are added and reduced. The expression number uses every letter, the soul urge only vowels and the personality only consonants. Accented letters count as their plain letter (É as E), and hyphens and apostrophes are ignored. These three numbers always use the Pythagorean table. The numerology name calculator also gives a Chaldean name number, using Cheiro's printed table (values 1 to 8, no letter carries 9): it adds every letter of the name, shows that compound total, and reduces it to one digit, as Cheiro works his own examples. Two-digit totals such as 11 or 22 stay visible as the compound number rather than being kept as master numbers. Our guide to Pythagorean vs Chaldean numerology shows both tables and why the results differ.

The letter Y counts as a vowel when no plain vowel (A, E, I, O, U) sits directly beside it, as in LYNN or the first letter of YVONNE, and as a consonant when one does, as in MAYA or YOLANDA. This follows the common rule that Y is a vowel when it sounds like one. You can override it on the soul urge and personality calculators.

Compatibility

Compatibility compares two life path numbers. Master numbers are read through their roots (11 as 2, 22 as 4, 33 as 6) with a note on what the master number adds. The tone of each pairing follows the traditional grouping of numbers into families: 1, 5 and 7; 2, 4 and 8; 3, 6 and 9.

Birth charts

Planet positions

Positions of the Sun, Moon and planets are computed with Astronomy Engine (MIT license), which models the solar system to about one arcminute. We use geocentric apparent positions on the true ecliptic of date, which is what astrological software reports. The North Node is the mean lunar node; the North Node calculator also shows the true node, the ascending node of the Moon's actual orbit at that moment.

How we tested it

We compared our calculator with the Swiss Ephemeris, the library behind most professional astrology software, on eight charts: Ulm 1879, London 1926, San Francisco 1955, Honolulu 1961, Buenos Aires 1975, Sydney 1990, Reykjavik 2000 and Tokyo 2024. Across all of them, every planet, the Ascendant, the Midheaven and all twelve Placidus house cusps agreed within 0.31 arcminutes, about a two-hundredth of a degree. These tests run automatically every time the site is built.

The single-placement calculators (rising sign, Moon sign, Sun, Moon and rising, Venus, Mars, Saturn return and North Node) have a second, independent test set of 93 checks. The Sun, Moon and Ascendant of fourteen people with documented birth data are compared with their published charts in Astro-Databank, including daylight saving time, local mean time before 1900 and births in the southern hemisphere; every one agrees within one arcminute. Sun, Moon, Venus, Mars and Saturn are compared with NASA's JPL Horizons ephemeris, within a fifth of an arcminute. The moments when the Moon, Venus or Mars changed sign during a birth date match Horizons within one minute, and 26 Saturn return passes, including seven returns with a retrograde triple pass, match Horizons within an hour. The mean and true lunar nodes are compared with the Swiss Ephemeris, within half an arcminute.

Time zones

A chart depends on the exact moment of birth in Universal Time, and this is where many calculators go wrong. We look up the time zone of your birthplace (for example America/Chicago) and apply its rules as they stood on your birth date, including daylight saving time and wartime changes, using the IANA time zone database built into your browser. Before a region adopted standard time, we use the local mean time of the city itself, calculated from its longitude, which is the convention of major astrology references.

If a clock time did not exist (skipped when clocks sprang forward) or happened twice (when they fell back), the result tells you. The offset we used is always shown with the chart.

Places

Our city list is built from GeoNames (licensed under Creative Commons Attribution 4.0) and includes about 34,000 places with a population above 15,000. It is stored on our site, so searching for your birthplace does not send your query to anyone. If your town is not listed, choose the nearest larger town in the same time zone: the difference in the chart is usually small, though it can move the Ascendant by a degree or so.

Houses, angles and signs

We use the tropical zodiac. The Ascendant and Midheaven come from local sidereal time and the true obliquity of the ecliptic. Houses default to Placidus; Whole Sign houses are available. Above roughly 66 degrees of latitude, Placidus cannot be calculated for some times, and we switch to Porphyry houses and tell you.

Aspects

We list the five major aspects with these orbs: conjunction and opposition 8 degrees, trine and square 7, sextile 5, with 2 degrees more when the Sun or Moon is involved.

Unknown birth time

Without a time we calculate for noon and leave out the Ascendant, Midheaven and houses. The Moon moves about 13 degrees a day, so we check whether it changed sign around your birth date and tell you if it did. The Moon sign calculator goes further: it checks the first and last minute of your birth date in local time and, when the sign changed, gives the local time of the change.

Interpretations

Our interpretation texts are original, written for Starvela to describe what numerology and astrology traditionally associate with each number and placement. They are for reflection and entertainment. We avoid predictions, guarantees and anything that could be read as health, financial, legal or relationship advice.

How personal readings are written

A personal reading starts with the same calculations as our free tools: every number and every planet, angle, house and aspect is computed from your birth details with the methods above, and printed in the reading so you can check it. Readings are composed with the help of AI writing tools, working from your computed chart and our interpretation guidelines. Each chapter works only from your calculated placements, follows written rules on tone and framing (no predictions, no fear, no health, money or legal advice), and is checked automatically against your chart before it is sent: a chapter that names a placement or number that is not in your chart is rejected and written again.

Our reading method has been reviewed and approved by a practicing astrologer. She reviewed the method: the calculations we use, the interpretation guidelines and the way readings are framed. She does not prepare, read or review individual orders.