Two reference points for twelve signs
The tropical zodiac places zero degrees Aries at the March equinox. A sidereal zodiac uses a reference tied to the stellar background. Both divide the zodiac into twelve equal signs of thirty degrees; neither is simply a map of the unequal astronomical constellations.
Anantrix uses a sidereal chart with Lahiri ayanamsa (the offset between tropical and sidereal positions) by default. Other sidereal conventions can produce slightly different degrees, especially important near a boundary.
A worked example
Suppose a tropical longitude is 130 degrees: 10 degrees into Leo. If the chosen ayanamsa is 24 degrees, subtracting it gives 106 degrees: 16 degrees into Cancer. This is a mathematical illustration using a rounded offset, not a claim about a particular person's chart or the exact offset on every date.
A sign does not always move back by one. A tropical longitude of 145 degrees, with that same 24-degree offset, becomes 121 degrees: both positions are in Leo. Calculate the degree rather than moving a sign name backwards by habit.
A Sun sign comparison is different from a Moon sign comparison
If a birthday website says Leo and a Vedic chart says Cancer Rashi, you may be comparing a tropical Sun sign with a sidereal Moon sign. There are two differences in that comparison: the planet and the zodiac. Compare Sun with Sun, or Moon with Moon, using identical birth details before drawing a conclusion.
Your ascendant also depends on the local horizon. Birth time, birthplace and historical timezone conversion matter alongside the zodiac setting. A daylight-saving error can change a time-sensitive placement even when both calculators use Lahiri.
How to compare two calculators
Check the date format, exact local clock time, birthplace, timezone and daylight saving. Then check tropical versus sidereal, the ayanamsa within a sidereal chart, and the house system. These settings answer different questions and should not be treated as interchangeable.
Agreement on astronomical positions checks the calculation method. It does not establish that an astrological interpretation or prediction will be true. Interpretive traditions differ, and a whole chart contains more information than one sign.
Put the explanation next to your own chart
Your free chart identifies the placements. When you want more detail, compare the scope of a personal astrology report or membership before choosing. The full chart and your birth-time confidence matter more than a single sign label.
Create my free birth chartReferences and method
Reviewed 30 September 2026. Astronomical definitions and traditional interpretation are described separately.