In Vedic astrology your rashi is your Moon sign - the sign the Moon actually occupied at the moment you were born, not the Sun sign a Western horoscope column asks for. This calculator finds it from your date, time and place of birth, along with your birth nakshatra, its pada and its ruling planet.
Two things separate a Vedic rashi from the star sign printed in a newspaper. The first is which body is read: Vedic astrology takes the sign of the Moon, not the Sun, as the chart's primary reference point - the janma rashi that the Vimshottari dasha, the gochara (transit) reckoning and most muhurta rules are all counted from.
The second is which zodiac is used. Vedic astrology measures from the fixed stars rather than from the equinox, subtracting the ayanamsha - currently about 24 degrees - from the tropical longitude. Because of that offset, a person's Vedic Moon sign is usually the sign immediately before the one a Western calculation would give. This tool uses the Lahiri (Chitrapaksha) ayanamsha, the standard in Indian practice.
The Moon is the fastest of the nine grahas, covering roughly thirteen degrees a day and changing sign about every two and a quarter days. On any given date there is therefore a real chance that the Moon crossed a sign boundary at some hour of that day - and a birth recorded as "the 14th" with no time can land on either side of it.
The calculator prints the Moon's exact degree within its sign, so you can see how close to a boundary the placement is. When it falls within one degree of an edge, it also states how long the Moon takes to cross at its own rate on that day, so you can judge whether your recorded time is precise enough for the answer to be safe.
Alongside the twelve rashis of thirty degrees each, the same circle is divided into twenty-seven nakshatras of 13 degrees 20 minutes. Each nakshatra is quartered further into four padas of 3 degrees 20 minutes, so a pada is one navamsa - one ninth of a sign.
Your birth nakshatra is the one the Moon occupied, and its ruling planet opens your Vimshottari dasha sequence: the proportion of the nakshatra the Moon had already crossed sets how much of that first mahadasha had already elapsed when you were born. That is why the nakshatra and its lord are shown here beside the sign.
For educational purposes. Astrological interpretations are traditional and not a substitute for professional advice.