What if I do not know my exact birth time?

This calculator will not cast a chart without one. An unknown time cannot be approximated — the lagna changes sign every two hours, so a guess produces a confidently wrong chart. Birth certificates and hospital records are the usual sources. Some astrologers perform birth time rectification from known life events, which is a separate discipline.

Why does my sun sign differ from what I have seen elsewhere?

Almost certainly because the other source is tropical (Western) and this is sidereal (Vedic). The two differ by the ayanamsa, about 24 degrees, so births in roughly the last third of a tropical sign fall in the previous sign sidereally.

Is the place of birth as important as the time?

For the lagna and the houses, yes. Latitude and longitude set the horizon, and longitude combined with the historical timezone determines the actual universal time of birth. Planetary positions in signs barely move, but the entire house structure depends on the location.

The kundali (birth chart)

A kundali is a diagram of where the planets stood, seen from one point on Earth, at one instant. Everything else in Vedic astrology is derived from it. Get the instant or the place wrong and every later calculation inherits the error, which is why this calculator asks for a birth time to the minute and refuses to guess one.

The lagna moves fastest

The ascendant — the lagna — is the zodiac degree rising on the eastern horizon. It advances through all twelve signs in roughly twenty-four hours, so it changes sign about every two hours and moves a full degree every four minutes. A birth time that is off by an hour usually produces a different lagna, and with it a different house for every planet. This is the single largest source of wrong charts, and no amount of computational precision downstream can repair it.

Sidereal, not tropical

Vedic astrology measures positions against the fixed stars. Western astrology measures them against the equinox, which drifts backwards through the constellations by about one degree every seventy-two years. The gap between the two systems is the ayanamsa, currently around 24 degrees. That is nearly a full sign: the same birth is very often a different sun sign in each system, and neither is wrong — they are measuring from different origins.

Where the numbers come from

Planetary positions here are read from Swiss Ephemeris data files, which derive from NASA JPL's DE431 ephemeris and are accurate to well under an arcsecond. When those files cannot cover a date, this calculator declines to cast the chart rather than falling back to the lower-precision analytical model that many free tools silently substitute. The Accuracy tab on any chart shows which engine answered, so the claim is checkable against whatever software you already trust.

Houses, and why the default is whole sign

A house system divides the chart into twelve fields of life. Whole sign — the classical Parashari method — makes each sign one house, with the rising sign as the first. It is the default here because it is what the classical texts assume. Placidus, Koch, Equal and Sripati are all available, and the Chalit tab shows where planets shift house between the whole sign chart and a cusp-based one, which is exactly where two astrologers reading the same birth tend to disagree.

Questions

What if I do not know my exact birth time?: This calculator will not cast a chart without one. An unknown time cannot be approximated — the lagna changes sign every two hours, so a guess produces a confidently wrong chart. Birth certificates and hospital records are the usual sources. Some astrologers perform birth time rectification from known life events, which is a separate discipline.
Why does my sun sign differ from what I have seen elsewhere?: Almost certainly because the other source is tropical (Western) and this is sidereal (Vedic). The two differ by the ayanamsa, about 24 degrees, so births in roughly the last third of a tropical sign fall in the previous sign sidereally.
Is the place of birth as important as the time?: For the lagna and the houses, yes. Latitude and longitude set the horizon, and longitude combined with the historical timezone determines the actual universal time of birth. Planetary positions in signs barely move, but the entire house structure depends on the location.

Cast this on a real chart

Enter a birth date, time and place and every calculation described here is available on the chart page.

Open the calculator

Ayanamsa — the sidereal offset — Lahiri, Raman, Krishnamurti and the rest. What the ayanamsa is, why it grows about a degree every 72 years, and how much your chart changes if you switch.
Navamsha — the D9 chart — The navamsha divides each sign into nine parts of 3°20'. What D9 shows about marriage, inner strength and whether a promising placement actually delivers.
Panchanga — Tithi, vara, nakshatra, yoga and karana — what each of the five limbs measures and how they are calculated from the Sun and Moon.