What is a natal chart and how is it calculated?

A natal chart (also called a birth chart or astrological map) is a diagram of the sky captured at the exact moment you were born: your date, time, and place. It shows where the Sun, Moon, and all the planets were, and divides them into 12 houses and zodiac signs. It's the foundational tool of Western astrology and the basis for almost every other reading: compatibility, transits, progressions, and solar returns.

How is a natal chart calculated?

The calculation is done with real astronomical ephemeris: tables that indicate the exact position of each planet in the ecliptic (the Sun's apparent orbit) at a given moment. The formula requires four pieces of data:

Birth date (day, month, year).
Exact time, ideally to the minute. If you don't know it, local noon is assumed and the chart is marked as "no-time chart".
Latitude and longitude of the birthplace. They determine the wheel's rotation (the Ascendant and Midheaven depend on them).

From there, astrology software cross-references planetary positions with house tables (Placidus, Whole Sign, Equal House, Koch) and produces a circular chart divided into 12 sectors.

The 4 parts of a natal chart

1. The planets and luminaries

The natal chart includes the Sun and the Moon (the luminaries) and the personal and social planets: Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. Chiron and the Lunar Nodes are sometimes added. Each one rules a dimension of your psyche: your essence (Sun), emotions (Moon), mind (Mercury), love (Venus), action (Mars), and so on.

2. The zodiac signs

The zodiac is a 360° band divided into 12 signs of 30° each. Each planet falls into a sign based on its position at your birth, and that sign colors how that planet expresses: your Sun in Aries is different from your Sun in Taurus, even though both are "Sun".

3. The 12 houses

The houses represent the areas of life: identity (House I), money (House II), communication (House III), home and family (House IV), romance (House V), health and service (House VI), partnership (House VII), transformation (House VIII), philosophy (House IX), career (House X), community (House XI), and spirituality (House XII). The sign on the cusp of each house and the planets inside it show how you experience that area.

4. The aspects

Aspects are the angles formed between planets. The main ones are:

Conjunction (0°): fusion of energies.
Trine (120°): natural harmony, talent.
Square (90°): tension that demands action.
Opposition (180°): polarity and projection.
Sextile (60°): gentle opportunity.

A chart with many trines is fluid and fortunate; one with many squares is dynamic and built through effort.

How to read your natal chart in 4 steps

Start with the Big Three: your Sun (essence), Moon (emotional world), and Ascendant (social mask). They're the executive summary of the whole chart.
Review the personal planets (Mercury, Venus, Mars): how you think, love, and act.
Look at the houses: in which life areas your most important planets fall. House X reveals vocation; VII, partnership; IV, roots.
Read the key aspects: start with the most exact (tightest orb). They reveal central tensions and gifts.

Do I need to know my exact birth time?

Not strictly. If you don't know it, the positions of the Sun, Mercury, Venus, and Mars don't change signs in a day. But the Moon moves 12° per day, and the Ascendant changes approximately every 2 hours. That's why a chart without a time can't show your ascendant or lunar house with precision. Even so, it offers a deep and useful map.

Calculate your natal chart for free

At Tu Verdad you can calculate your natal chart in seconds. Enter your date, time, and city (or use the interactive map) and get an interactive chart with your zodiac wheel, planetary positions, aspects, houses, and a complete interpretation in Spanish or English. Everything is calculated with the astronomical library circular-natal-horoscope-js, the same one used by professional astrologers.

→ Calculate my natal chart now