If you've checked your moon sign on a Western astrology app before and gotten a different answer here, you haven't made a mistake — you're looking at two different measuring systems. Western (tropical) astrology anchors the zodiac to the seasons, starting Aries at the spring equinox every year. Vedic (sidereal) astrology, which this calculator uses, anchors the zodiac to the actual, fixed positions of the constellations in the sky.
Over centuries, the slow wobble of Earth's axis — a phenomenon called precession — has pushed these two systems apart by roughly 24 degrees, an offset known as the ayanamsa. In practice, this means your Vedic (Rashi) moon sign is often the sign just before your Western tropical moon sign. Neither is "wrong": tropical astrology reads your relationship to the seasons, while sidereal astrology reads the Moon's true placement against the stars. This calculator uses the Lahiri ayanamsa, the standard reference in Jyotish, to give you your authentic Chandra Rashi.