Cancer and Leo compatibility starts with a fact no other pair can claim. The Moon rules Cancer. The Sun rules Leo. So this couple joins the signs of the two lights, the two brightest bodies in the sky. In the oldest rulebook of Western astrology, these two signs are where the whole map of rulers begins.
That is the thread of this page. We counted how common the pair is in US births. About 1 random US couple in 63 is a Cancer with a Leo. Then we counted real charts. In about 1 couple in 6, one partner has the Moon in the other’s Sun sign. And that partner was always born within five and a half days of a new Moon. Each number comes with its method, so you can check it.
The short answer, in six lines
| Question | What we found. |
|---|---|
| How common is a Cancer and Leo couple? | About 1 random US couple in 63, or 1.58 percent. |
| Where does it rank among the 78 pairs? | Second, just behind Leo and Virgo. |
| How far apart are the signs? | One sign, or 30 degrees. They sit side by side. |
| What ties them in the old books? | Their rulers, the Sun and the Moon, and not an aspect. |
| How many couples have one Moon in the partner’s sign? | In about 1 couple in 6, always near a new Moon. |
| Did real marriages favor the pair? | By half a percent, a gap the author traced to form errors. |
First, what no one can promise
Astrology is not a science. No study has shown that a Sun sign predicts how a couple will do. The largest test we know of was run by David Voas, then at the University of Manchester, in 2007. He used the 2001 census of England and Wales. It holds the birth dates of more than 10 million married couples.
He asked a plain question. Do some sign pairs marry more than chance allows? His answer was no. He also found why some raw counts looked odd. Too many couples shared a sign, because a clerk or a spouse wrote the same birthday twice. Once he took out those errors, the table looked random. The Skeptical Inquirer reported his result in March 2008.
Here are the Cancer and Leo cells from his corrected table, Table 7. It holds 9.5 million couples.
| Couple in the 2001 census | Found | Expected by chance | Gap. |
|---|---|---|---|
| Cancer wife, Leo husband. | 67,834 couples. | 67,520 couples. | 314 more. |
| Leo wife, Cancer husband. | 68,095 couples. | 67,690 couples. | 405 more. |
| Both kinds together. | 135,929 couples. | 135,209 couples. | Half a percent more. |
The expected count is what you get if people pick partners with no regard to sign. Both cells sit a little above it. Is that a sign that Cancers and Leos seek each other out? Voas answers that himself. He notes that the cells next to the same sign line are almost all above chance. Cancer and Leo is one of those cells, since the signs are neighbors.
His reason is simple. Some forms still gave both spouses the same birth month. A couple born in the same month can land in two signs side by side. His fix removed most of that error, but not all of it. So the small excess shows up again for every pair of neighbors. It is a trace of the paperwork, not of the stars.
He adds that a cell can drift up to 450 from chance by luck alone. Both Cancer and Leo cells stay inside that line. So this page reads the pair as a lens, not a forecast. The lens gives two people words for how each one works. The two people decide the rest.
How common is a Cancer and Leo couple?
Your Sun sign is the slice of the sky the Sun stood in when you were born. There are twelve slices of 30 degrees each. Cancer season runs from about June 21 to July 22. Leo season runs from about July 22 to August 22.
The signs are not equal in births. Two things set the count. The first is how long the Sun stays in each sign. The second is how many babies are born per day in that part of the year. Both signs win on both counts.
Earth is farthest from the Sun in early July. In 2026, that point fell on July 6, with the Sun at about 15 degrees of Cancer. Far from the Sun, Earth moves at its slowest. So the Sun seems to crawl through the summer signs. We timed each stay for every year from 1600 to 2400, the site’s reference window.
| Sign | Time the Sun spends there | Rank of twelve. |
|---|---|---|
| Cancer. | About 31.45 days. | First, the longest stay. |
| Gemini. | About 31.33 days. | Second. |
| Leo. | About 31.29 days. | Third. |
| Capricorn. | About 29.45 days. | Last, the shortest stay. |
US births also peak in late summer. Put the two effects together and you get the share of births in each sign. We used two public files of daily US births.
| Question | Social Security file, 2000 to 2014 | Health Statistics file, 1994 to 2003. |
|---|---|---|
| Births in the file. | 62.2 million births. | 39.7 million births. |
| Share born with the Sun in Cancer. | 8.84 percent, third of twelve. | 8.87 percent, third of twelve. |
| Share born with the Sun in Leo. | 8.96 percent, first of twelve. | 8.96 percent, first of twelve. |
| Chance a random pair is one Cancer and one Leo. | 1.58 percent, or 1 pair in 63. | 1.59 percent, or 1 pair in 63. |
Why multiply by two? A couple can be a Cancer woman with a Leo man, or the other way round. Both count. So the chance is two times the Cancer share times the Leo share. If every sign held one twelfth of births, the pair would show up once in 72 draws. It shows up once in 63.
There are 78 ways to pair the twelve signs, same sign pairs included. Cancer and Leo come second. Only Leo and Virgo is more common, at 1 in 62. Our page on Leo and Virgo compatibility gives the full ranking. In the older file, the gap between the two pairs shrinks to a hair.
None of this comes from the stars. It comes from the calendar and from the months when US babies are born. A common pair is not a better pair. It is a pair you are more likely to meet.
Next door, yet turned away
Place the twelve signs on a wheel. Cancer and Leo sit side by side, one sign or 30 degrees apart. Modern books call that link a semi-sextile and rank it as a minor aspect. An aspect is a set angle between two points in the sky that astrologers read as a link.
What Ptolemy says about neighbors
Claudius Ptolemy wrote the Tetrabiblos in Alexandria around 150 AD. It is the oldest full textbook of Western astrology. We read Book 1 in the English version by Frank Robbins, from 1940. In chapter 13 he lists four aspects: the opposition, the trine, the square and the sextile. Signs one apart form none of them.
He then names two more kinds of tie. Signs “command” and “obey” when they sit the same distance from the spring or fall point. Signs “behold” each other when they sit the same distance from a solstice point. Readers take this in two ways. Robbins, in his note 83, reads it by whole signs. William Lilly, in Christian Astrology in 1647, reads it degree by degree. On the whole sign reading, Leo beholds Gemini, and Cancer has no partner at all. On the degree reading, each degree of Cancer finds its mirror in Gemini, and each degree of Leo finds its mirror in Taurus. So neither reading ties Cancer to Leo.
That leaves chapter 16. Ptolemy calls signs with no tie at all “disjunct” and “alien.” He says they are one or five signs apart. Of the ones next door, he writes that they “are as it were averted from one another.” In plain words, the two signs face away from each other.
How close are the two Suns in real couples?
A sign is a slice, so the label does not fix the angle. A late Cancer and an early Leo can have Suns almost on top of each other. An early Cancer and a late Leo can be almost 60 degrees apart. We weighed each degree by real US births and paired every Cancer with every Leo.
| What the two Suns form, in degrees | Share of Cancer and Leo pairs. |
|---|---|
| A semi-sextile within 3 degrees. | 19 percent, about 1 pair in 5. |
| A semi-sextile within 6 degrees. | 36 percent, about 1 pair in 3. |
| A semi-sextile within 10 degrees. | 56 percent, just over half. |
| Suns within 8 degrees of each other. | 3.6 percent, about 1 pair in 28. |
The leeway allowed around an exact angle is called the orb. These shares match our other pair pages. The width of a sign sets them, not the pair. For an exact semi-sextile, the two birthdays must fall about 31.3 to 31.5 days apart. In 2026, the Sun reached 15 degrees of Cancer on July 6 at 9:57 p.m., New York time. It reached 15 degrees of Leo on August 7 at 7:43 a.m., New York time.
The houses of the two lights
So the old aspect rules give this pair nothing. Their rulers give them almost everything. In chapter 17, Ptolemy explains why each planet owns the signs it owns. He starts with these two.
He writes that Cancer and Leo are the most northern signs. They are the closest to our zenith, the point straight overhead, and so “most productive of heat and of warmth.” So they were given “to the luminaries,” the Sun and the Moon. Leo, a male sign, went to the Sun. Cancer, a female sign, went to the Moon.
Then he builds the rest of the map out from that seam. The half of the wheel from Leo to Capricorn is the Sun’s half. The half from Aquarius back to Cancer is the Moon’s half. Each of the five planets gets one sign in each half. Mercury gets the two signs next to the lights, Virgo and Gemini. Venus gets the next two, Libra and Taurus. Then Mars, Jupiter and Saturn follow, in the order of their spheres.
| Planet | Its home on the Sun’s side | Its home on the Moon’s side. |
|---|---|---|
| The Sun and the Moon. | Leo, for the Sun. | Cancer, for the Moon. |
| Mercury. | Virgo. | Gemini. |
| Venus. | Libra. | Taurus. |
| Mars. | Scorpio. | Aries. |
| Jupiter. | Sagittarius. | Pisces. |
| Saturn. | Capricorn. | Aquarius. |
Read the table as a fold. Cancer and Leo sit on the crease. Every other pair of homes mirrors across it. No other two signs hold that place. So the tradition does not tie Cancer and Leo by angle. It ties them as the two halves of one root.
One ruler always home, one almost never
A planet is at home in the sign it rules. Leo is ruled by the Sun, and every Leo has the Sun in Leo. So every Leo has its ruler at home, 100 percent of the time. Our Leo sign page shows that no other sign can say this.
Cancer is ruled by the Moon, the fastest body in the chart. The Moon laps the zodiac in about 27 days. It sits in Cancer for only 8.20 percent of Cancers, over 800 years of sky. That is the lowest figure of all twelve signs. Our Cancer sign page tells that side of the story.
So this pair holds both ends of the table, top and bottom. Every Cancer and Leo couple has at least one ruler at home, the Leo’s Sun. Both rulers are home in only about 1 couple in 12.
The Moon swap happens only near a new Moon
Here is the measure that belongs to this pair alone. The Moon sign shows what makes a person feel safe. Astrologers pay close heed when one partner’s Moon sits in the other’s Sun sign. For this couple, that means a Leo with the Moon in Cancer, or a Cancer with the Moon in Leo.
The Moon’s place is tied to the Sun’s place by the phase. A new Moon is the moment the Moon passes the Sun. Just before it, the Moon sits a little behind the Sun on the wheel. Just after it, the Moon sits a little ahead.
So a Leo can have the Moon in Cancer only in the last days before a new Moon. The Moon is then one sign behind the Sun. A Cancer can have the Moon in Leo only in the first days after a new Moon. The Moon is then one sign ahead. We checked this for every two hours from 1600 to 2400.
| Born with | Share of that Sun sign | Time from the new Moon. |
|---|---|---|
| The Sun in Leo, the Moon in Cancer. | 8.26 percent of Leos. | From 0 to 5.5 days before it, 2.4 days at the middle value. |
| The Sun in Cancer, the Moon in Leo. | 8.28 percent of Cancers. | From 0 to 5.5 days after it, 2.4 days at the middle value. |
| The Sun in Cancer, the Moon in Cancer. | 8.20 percent of Cancers. | Close to a new Moon as well. |
Each share is close to one in twelve. The Moon spends about the same time in every sign. What is rare is not the share. It is the timing. The swap cannot happen at a full Moon, or at a half Moon. It is locked to the dark of the Moon.
A real example from 2026
The new Moon of July 14, 2026, came at 5:44 a.m., New York time, with the Sun in Cancer. The Moon entered Leo that evening, at about 6:40 p.m. So a Cancer born between that moment and about 8:10 p.m. on July 16 has the Moon in Leo. The window lasts about two days.
The mirror window came in August. From about 3:50 a.m. on August 9 to about 4:40 a.m. on August 11, a Leo baby got a Cancer Moon. The next new Moon came on August 12 at 1:37 p.m. That new Moon was also a total eclipse of the Sun, seen from Greenland, Iceland and Spain.
What this means for couples
Take a random Cancer and a random Leo. We treated their charts as unrelated, which is what the Voas census showed for signs.
| What the couple has | Share of Cancer and Leo couples. |
|---|---|
| At least one Moon in the partner’s Sun sign. | 15.9 percent, or about 1 couple in 6. |
| Both Moons in the partner’s Sun sign. | 0.68 percent, or about 1 couple in 146. |
| The same Moon sign in both charts. | 8.3 percent, or about 1 couple in 12. |
So in about 1 Cancer and Leo couple in 6, one partner carries the other’s sign as a Moon. That partner was born in the dark days around a new Moon. If you are in such a couple, you can check it. Look up your birth date in a Moon phase table. You will find a new Moon within five and a half days.
Both lights at home
A Leo with the Moon in Cancer has one more trait. Both lights sit in their own signs, the Sun in Leo and the Moon in Cancer. Only a Leo can have that, since the Sun must be in Leo. About 1 Leo in 12 does.
The old writers knew this layout well. The Roman writer Firmicus Maternus, in Book 3 of his Mathesis, gives a chart for the birth of the world. It puts the Moon in Cancer and the Sun in Leo. Chris Brennan covers this chart, the Thema Mundi, in his Hellenistic Astrology from 2017. It was a teaching chart, not a real sky. Still, it shows the same fold as Ptolemy’s table.
The rest of the dignity table
Each planet has signs where the old books call it strong and signs where they call it weak. These ranks are called dignities. A planet is in exile in the sign across from its home. It is exalted in its sign of honor. It is in its fall in the sign across from that honor.
| Planet | In Cancer | In Leo. |
|---|---|---|
| The Moon. | At home. | No major rank. |
| The Sun. | No major rank. | At home. |
| Jupiter. | Exalted. | No major rank. |
| Mars. | In its fall. | No major rank. |
| Saturn. | In exile. | In exile. |
| Venus. | No major rank. | No major rank. |
| Mercury. | No major rank. | No major rank. |
The table shows the four big ranks only: home, exile, honor and fall. One row stands out. Saturn is in exile in both signs. That follows from the fold. Saturn got the two signs across from the lights, Capricorn and Aquarius. Ptolemy says Saturn is cold, the reverse of the Sun’s heat. He adds that its facing of the lights “is not consistent with beneficence.”
In a reading, Saturn stands for limits, time and duty. The old view is that a planet in exile still works. It works as a guest in a hostile house. So the tradition would say this pair does not welcome Saturn on either side. It is a pair of warmth, in the old picture, with little room for cold rules.
Leo has no planet exalted there, and so no planet in its fall. Cancer has both: Jupiter is honored there, and Mars falls. Our page on the Moon in Cancer explains why the Moon is at home in Cancer, not exalted.
How the pair can play out day to day
Here the page turns from counts to tradition. What follows is how astrologers read the two signs. Treat it as a set of images to test against your own life, not as facts about any person.
What each partner brings
Cancer is a water sign that starts a season. Water stands for feeling, memory and care. In the old picture, the Moon reflects light and holds a mood. A Cancer partner shows love by looking after people. A meal kept warm. A text to ask if you got home. A room that feels safe to come back to.
Leo is a fire sign in the middle of a season. Fire stands for heat, drive and pride. The Sun gives its own light. A Leo partner shows love out loud. A big plan for a birthday. Praise in front of friends. A steady warmth that others can lean on.
Where they meet
The two lights share one job in the old books: they give life. The Sun gives heat and the Moon gives moisture, in Ptolemy’s terms. So both partners are, in this reading, builders of a home and of a family life. One keeps the hearth. The other lights the room.
Where they rub
The friction comes from the two kinds of light. One shines outward. The other shines back what it gets.
| Where it snags | What Cancer feels | What Leo feels | A small step that helps. |
|---|---|---|---|
| Praise. | Unseen when care is taken for granted. | Unseen when praise stays private. | Say one thank you out loud each day. |
| Mood. | Hurt that goes quiet and turns inward. | Shut out by a silence with no reason. | Name the hurt in one short line, the same day. |
| Social life. | Drained by too many nights out. | Dimmed by too many nights at home. | Trade one night out for one night in. |
| Pride. | Stung when a joke lands on the family. | Stung when a plan gets no applause. | Ask what the other needs to hear. |
None of these steps needs a chart. Any two people with different styles can use them. The signs only give a name to the pattern. The fix lives in plain talk.
Look past the Sun
A Sun sign is one point in a chart with ten planets and twelve houses. To read two people well, astrologers compare whole charts. That method is called synastry. It looks at how each planet in one chart meets each planet in the other.
For this pair, start with the Moons. Check the two birth dates in a Moon phase table. A birth close to a new Moon tells you to look for the swap. Then look at Venus, the planet of taste and affection. Our page on Cancer and Leo Venus placements reads the same two signs through Venus instead of the Sun.
If a birthday falls near a sign change, check it first. The guide to the 12 zodiac signs gives the real Sun dates for each sign. A July 22 birthday can be Cancer in one year and Leo in the next.
How we measured this
You can redo each number on this page.
For the Sun sign shares, we used two daily birth files published by FiveThirtyEight. One comes from the Social Security Administration and covers 2000 to 2014. The other comes from the National Center for Health Statistics and covers 1994 to 2003. We found each moment the Sun changed sign with astronomy-engine, an open source sky library, in the tropical zodiac. We spread each day’s births evenly over its 24 hours in Chicago time. When the Sun changed sign that day, we split the births by the hours before and after.
For the pair rate, we assumed that partners’ birth dates are not linked, which is what Voas found. The chance of one Cancer and one Leo is then two times the Cancer share times the Leo share. For the ranking, we did the same for all 78 pairs.
For the census cells, we used Table 7 of the Voas paper. It leaves out couples with a birthday on the first of a month, since too many of those dates came from blanks the census office filled in. It also removes the excess of same sign couples. The expected count for each cell is the row total times the column total, divided by the grand total. His Table 8 shows the same gaps, in hundreds.
For the Sun stays, we timed the Sun into each sign for every year from 1600 to 2400, by two separate routes, astronomy-engine and the Swiss Ephemeris. For the orbs, we took the Sun’s place at each birth day of the Social Security file. Then we paired every Cancer day with every Leo day, weighted by births.
For the Moon, we took the place of the Sun and the Moon every two hours from 1600 to 2400. That is 3,506,328 moments. We kept the moments with the Sun in Cancer or Leo and counted the Moon’s sign. For each moment with the swap, we searched for the nearest new Moon and timed the gap. As a second route, we ran a separate grid every five hours, offset by 97 minutes, with a different way to compute both bodies. The two routes agree within 0.03 point on every share. The Moon in Cancer comes out at 8.20 percent of Cancers, which matches the figure on our sign pages.
For the couple shares, we combined the Cancer and the Leo results as two unrelated charts. For example, the chance that neither Moon sits in the partner’s sign is 91.74 percent times 91.72 percent. One minus that gives 15.9 percent. The 2026 windows come from a scan every ten minutes, so each time is good to about ten minutes. Times are given in New York time.
For the old rules, we read Ptolemy’s Book 1, chapters 13 to 17, in the Robbins version, with his notes. We checked the dignities against Lilly.
Frequently asked questions
Are Cancer and Leo compatible?
Astrology reads them as neighbors with no classic aspect, tied instead by their rulers, the Moon and the Sun. No study has shown that any sign pair lasts longer, so treat it as a lens, not a forecast.
How common is a Cancer and Leo couple?
In US birth data, about 1 random pair in 63 is one Cancer and one Leo. That puts it second of the 78 sign pairs, just behind Leo and Virgo.
Why are Cancer and Leo called the signs of the lights?
Ptolemy gave the two warmest signs to the two lights. Leo went to the Sun and Cancer went to the Moon. He then placed every other planet’s homes out from those two signs.
Can a Leo have a Cancer Moon?
Yes, about 1 Leo in 12 does. That Leo was always born in the last five and a half days before a new Moon. Such a chart has both lights in their own signs.
What aspect do Cancer and Leo form?
By sign, a semi-sextile of 30 degrees, a minor aspect. Ptolemy called signs one apart averted, meaning turned away. By degree, the Suns can sit from almost 0 to almost 60 degrees apart.
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