Guides ยท Tools
Big three calculator: your Sun, Moon and rising sign
Enter your birth date, birth time and the city you were born in. We work out where the Sun and Moon were and which sign was rising over the eastern horizon at that minute, and show you all three free, in about two minutes.
Free. No card. Don't know your birth time? You can still start: tap roughly when, or "I have no idea".
What the calculator needs, and why
Each of the three signs depends on a different part of your birth details. That is why a Sun sign takes one date, and a rising sign takes the exact minute and the place.
| You enter | What it decides | What happens if it's missing |
|---|---|---|
| Birth date | Your Sun sign, and most of the time your Moon sign | Nothing can be worked out |
| Birth time | Your rising sign, your houses, and your Moon sign on days the Moon changes sign | No rising sign; the Moon is checked across the whole day |
| Birth city | The time zone your city used that day (daylight saving included) and the horizon your rising sign is read from | The time can't be turned into one exact moment |
The city matters more than people expect. 7:00 in the morning in Chicago and 7:00 in the morning in London are six hours apart, and each has its own eastern horizon. We look up the time-zone rules your city had on the day you were born, so a summer birth in 1985 and a winter birth in 2001 are both turned into the right moment.
How it works it out
Your date, time and city become one exact moment. For that moment we calculate where the Sun, the Moon and eight planets were, seen from Earth, using astronomy-engine, an open-source astronomy library. The signs are the tropical zodiac most Western astrologers use. Your rising sign is the sign coming up on the eastern horizon over your birthplace at that minute, and houses use the Placidus system, the most common one. The whole method is on how we work out your chart.
This is the same sky an astronomy program would show you. What the positions mean is astrology, offered for entertainment.
How sure is each answer?
Sun sign: almost always certain
The Sun changes sign once a month, around the 19th to the 23rd. If you were born on one of those days, the exact year and time decide it, which is why a newspaper horoscope can give you the wrong sign while a calculator gives you the right one.
Moon sign: certain on most days
The Moon moves through a whole sign in about two and a half days. On most birthdays it stays in one sign from midnight to midnight, so your date alone settles it. On the days it changes sign, your birth time decides which side you fall on. If your Moon changed sign on your birthday and you don't know the time, the free result says so, so you know which answer to trust.
Rising sign: needs the minute
A new sign rises about every two hours, faster or slower depending on how far north you were born. Four minutes moves the rising point by about one degree. A time from your birth certificate or hospital record is the best source; "around lunchtime" from a parent can still be enough if you weren't born near a change.
If you don't know your birth time
You can still use the calculator. On the time screen, tap morning, afternoon, evening or late night, or "I have no idea". With a rough time, we place the planets at the middle of that window and check your Moon across the whole of it, so your Sun and Moon still come back, and we tell you plainly that the rising sign needs the exact time. Where to look for it, and what a chart says without it, is in finding your rising sign without a birth time.
- Your birth certificate (in many US states the long form lists the time)
- The hospital record or your baby book
- A parent's or relative's memory, which is often good to the hour
What you get free, and what's paid
The calculator is free: your chart wheel, your Sun, Moon and rising signs, and a short read of each. You don't need a card, and you can stop there.
If you want more, the full reading is $9.99 once and nothing renews: every planet in its sign and house, the patterns between them, and what your chart says about love, work and the people around you. It is written for your chart, not for your Sun sign alone.
What to do with your big three
Read them as three answers to three questions. The Sun is what you are building and what makes you feel most like yourself. The Moon is what you need to feel okay, and how you react before you think. The rising sign is how people first see you and how you start new things. Two people with the same Sun sign often feel nothing alike because their Moon and rising differ. For all twelve signs in each role and a four-step way to read the three together, see big three astrology meaning.
Questions
Is this calculator free?
Yes. Your Sun, Moon and rising signs and the chart wheel cost nothing and need no card. Only the full written reading is paid, $9.99 once.
Why is my rising sign different from another site's?
Usually because of the time or the time zone: a time entered as PM instead of AM, a city that used daylight saving that year, or a birth near the moment the rising sign changed. Check the time you entered first.
Do I need an account?
No. You give an email only so we can send you your chart; you can unsubscribe in one tap.
About two minutes. Free, no card.
More on reading a chart: the guides.