Mars Sign Calculator

What is a Mars sign?

Your Mars sign is the zodiac sign Mars was in at the moment you were born. Mars takes about two years to travel around the zodiac, so it usually spends six to eight weeks in each sign. About every 26 months it turns retrograde for roughly ten weeks, and around those periods it can stay in a single sign for up to seven months.

Unlike Venus, Mars can be anywhere in relation to the Sun, so your Mars sign may have nothing in common with your Sun sign. A gentle Pisces Sun with Mars in Aries, or a fiery Leo with Mars in Virgo, are common combinations, and they often explain why someone acts quite differently from what their Sun sign would suggest.

What your Mars sign describes

Astrologers associate Mars with drive and action: how you go after what you want, how you assert yourself, compete and handle conflict, how anger shows up, and what fires your desire. If Venus is how you attract, Mars is how you pursue. It is also read as your physical energy and the way you start things. In traditional astrology Mars rules Aries (and, in the older system, Scorpio) and is exalted in Capricorn, where its drive is said to be at its most disciplined.

The element of your Mars sign is a useful first clue. Fire Mars (Aries, Leo, Sagittarius) is often described as bold and spontaneous; earth Mars (Taurus, Virgo, Capricorn) as persistent and practical; air Mars (Gemini, Libra, Aquarius) as strategic and verbal; and water Mars (Cancer, Scorpio, Pisces) as emotionally driven and intuitive. Your Mars sign does not decide how you behave. It describes a style of energy you can learn to use well, and reflecting on it can help you notice where your drive flows easily and where it gets stuck.

Birth time, cusps and retrograde Mars

Mars moves less than a degree a day, so on almost every date your Mars sign is the same whatever time you were born. You can tick “I don’t know my birth time” and still get a definite answer, and a birth time you only know roughly is rarely a problem. On the few days a year when Mars changes sign, the calculator checks your whole birthday and shows the local time of the change and both possible signs.

When you enter a time and Mars changed sign within a day of your birth, the result says so, with the date and time of the change. It also tells you if Mars was retrograde. Astrologers often read a retrograde Mars as energy that turns inward first: more reflective, strategic or self-questioning before it acts. About 9% of people are born with it, and it is a nuance rather than a weakness.

How ReYep calculates your Mars sign

Your local birth time is converted to Universal Time with the full IANA time zone history of your birth place: every summer-time rule in force on that date, and the many historical changes countries have made, including Turkey’s in the 1970s, 1980s and 2016. If your time falls in an hour that was skipped or repeated when clocks changed, the calculator tells you and shows whether the other reading would change your sign.

Mars’s position comes from the open-source Astronomy Engine library: its apparent geocentric position, corrected for light time and aberration, in the tropical zodiac on the true ecliptic and equinox of your birth date. Retrograde motion is read from the change in longitude over the 24 hours around your birth. In our tests against Swiss Ephemeris at 1,000 random moments between 1920 and 2060, the largest difference for Mars was 0.003°, and the direction of motion matched every time Mars was clearly moving. Every step is shown under “Calculation details”, and nothing leaves your browser.