☿ Free Mercury Sign Calculator
Umbriel's free Mercury sign calculator finds your natal Mercury (its sign, exact degree and house) from your birth date, time and place.
Free, no account, no email. Runs in your browser.
14160+ people cast their chart here in the last 30 days.
No account, no email. Mercury is never more than about 28° from the Sun, so your Mercury sign is always your Sun sign or the one on either side of it.
- What you'll needBirth date (time and place for the house)
- What you getYour Mercury sign and exact degree, the house it falls in, whether it was retrograde, and every aspect it makes
- CostFree, no account required
What a Mercury sign is
Your Mercury sign is where Mercury stood at your birth. It is traditionally associated with the mind in motion: how you think, speak, learn, argue, joke and sort things out. Older astrology also gives Mercury trade, errands, siblings and short journeys, which is a less flattering list and often a more recognisable one.
Deeper.a cup-of-tea read
Mercury never strays far from the Sun. Its orbit sits well inside Earth's, so seen from here it can only reach about 28° from the Sun at most, and usually less. That means your Mercury is in your Sun sign or one of the two neighbouring signs, always. It is a useful sanity check: a Mercury three signs from your Sun is a mistake, not a placement. It also means Mercury is only ever seen low in the sky at dawn or at dusk, which is why the old texts call a Mercury that rises before the Sun a morning star and one that sets after it an evening star, and read the two differently.
Its pace is the most uneven of any planet. Direct and moving well, Mercury can cross a sign in a fortnight, at more than two degrees a day. But it turns retrograde about three times a year for roughly three weeks each time, so it spends close to a fifth of its life appearing to move backwards, and a sign it retrogrades through can hold it for two months. A natal Mercury retrograde is common, about one person in five, and is traditionally read as a more inward, reconsidering way of thinking, not as a fault in it.
How Umbriel computes it
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Your Mercury sign is the zodiac sign that Mercury was in, seen from Earth, at your birth moment. Umbriel computes Mercury's position from a planetary theory for the day number of your birth, converts it to a geocentric ecliptic longitude using the Sun's position, and reads the sign as the longitude divided by 30, with the degree as the remainder. Whether Mercury was retrograde is taken from its motion across a half-day step around your birth moment, and its daily speed is kept. Your birth time is turned into UT through the IANA time-zone database, so date, time and place fix the moment. The house is the only part that needs an exact birth time and place: it comes from the cusps of your chosen house system, and without a birth time Umbriel gives no house at all. The sign does not depend on the birthplace, and it depends on the time only if Mercury changed sign on your birthday, which Mercury does more often than any other planet because it moves so fast. Where that is the case Umbriel says so, and names both signs rather than picking one.
What's in your result
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- Sign and exact degreeTo the degree and minute, which matters more for Mercury than for any other planet, because it crosses sign boundaries so quickly.
- The house it falls inWhere the Mercury business tends to show up. This is the part that needs your birth time.
- Retrograde or directWhether Mercury was moving forward at your birth, and how fast, including the near-station slowness either side of a turn.
- Every aspect it makesEach contact with its exact orb, and whether it was applying or separating.
- Its distance from the SunHow far Mercury sat from the Sun: morning star or evening star, and whether it was close enough to be combust or sitting at the very heart of the Sun, cazimi.
- The sign's rulerWhere Mercury's dispositor sits. The placement the whole Mercury story answers to.
Don’t know your birth time?
Deeper.a cup-of-tea read
Know it roughly? Give the time and say where it came from (a certificate, a parent’s memory, or something rough like “early morning”), and your chart tells you what could change within that window.
Don’t know it at all? Umbriel does not fill the gap with a guess. Tick “I don’t know the time at all” and it checks your whole birthday, hour by hour, then tells you two things: which placements are the same whatever time you were born, as exact as they would be if you knew the minute, and which are down to two signs, both named, so you know what a parent’s memory would settle.
The Ascendant, the Midheaven and the houses are left out rather than approximated. A birth time is the one thing they cannot be computed without, and an approximate Rising sign that looks exact is worse than no Rising sign at all.
Common questions
Can I find my Mercury sign without a birth time?
Usually, yes. Mercury spends somewhere between two weeks and two months in a sign, so the date is usually enough. The exception is a birth on or near the day Mercury changed sign, which happens more often than for any other planet, and there the hour decides it. Umbriel checks, and names both signs when the day is split. What you cannot get without a time is the house, and Umbriel leaves that blank rather than guessing.
What does the Mercury sign mean?
It is traditionally read for the mind in motion: how you think, how you talk, how you learn and how you argue. Many people find it describes their speaking style and sense of humour better than their Sun sign does. Best held as a prompt to think with, not a rule about you.
What does it mean if my Mercury is retrograde?
It means Mercury appeared to move backwards at your birth, which it does about three times a year for roughly three weeks, so around one person in five has it. It is traditionally read as a more inward, considered or roundabout way of thinking. It is not a flaw, and it has nothing to do with the retrograde happening in the sky this month.
Why is my Mercury sign the same as my Sun sign?
Because it very often is. Mercury can never be more than about 28° from the Sun, which is less than one sign's width, so your Mercury is in your Sun sign or one of the two beside it, and the same sign roughly half the time. That is a property of its orbit, not a rule of astrology.
Is this Mercury sign calculator free?
Yes: sign, degree, house, retrograde status and aspects, with no account and no email, calculated in your own browser.
What if I don’t know my birth time?
Umbriel checks your whole birthday hour by hour and separates what is certain from what is not. Placements that are the same whatever time you were born are shown as exact. Placements that changed sign during the day are shown as two named signs, so you know what a parent's memory would settle. The Ascendant, Midheaven and houses are left out rather than approximated. They cannot be computed without a time, and an approximate Rising sign that looks exact is worse than none.
Do I need an account or an email address?
No. There is no sign-up, no email capture and no free trial. Enter your details and the result is drawn in your own browser.
Go deeper
Every one of these is a page in its own right, written out one at a time.
Related free tools
Next doorMercury Return CalculatorUmbriel's free Mercury return calculator finds the exact dates Mercury comes back to the degree it held at your birth, about once a year as seen from Earth.Prints in the head of this page, all public domain except where stated: Mercury, plate 42 from Planets and Spheres, Master of the E-Series Tarocchi, c. 1465, Art Institute of Chicago; Urania's Mirror, Sidney Hall, 1825, Library of Congress via Wikimedia Commons; Johannes Hevelius, Machina coelestis, Danzig, 1673, Houghton Library. Ground: Andreas Cellarius, Harmonia Macrocosmica, 1661, Wikimedia Commons.
Further down the page: Sebald Beham, Mercury, plate six from The Seven Planets with the Zodiacs, 1539, Art Institute of Chicago. The next-door print comes from that page's own head. The pointing hand: a pointing hand, after a medieval manuscript margin (line art by Jerimee).
Umbriel offers every system here as a set of prompts to think with, never as a statement of fact about who you are. Take what's useful, leave the rest.