In short
In astrological tradition, two Aries are a couple of one element (Fire) and one cross (cardinal): both are used to going first and argue over who leads. A check of 10 million marriages from the 2001 census of England and Wales did not find that people with “compatible” Sun signs married more often than chance would predict. The Sun sign is one point out of a dozen: the Moon, Venus and Ascendant of two Aries can differ, so it is more honest to calculate the couple from two full dates of birth.
What is known for certain: elements, crosses, rulers
These are definitions of astrology, not a conclusion about the couple: they are the same in all schools.
Aries is the sign the Sun occupies roughly from March 21 to April 20; the boundary shifts by a day from year to year. So “two Aries” are two people whose birthdays fall within this month, regardless of the year and time of birth.
What tradition says
In Western astrology, two identical signs form a conjunction: similarity without complement. Two Aries share the element of Fire (impulse, speed), the cardinal cross (starting rather than finishing) and the ruler Mars (directness, rivalry).
Hence the typical description of the couple by popular astrologers: the argument over who leads flares up in the first months of knowing each other, not years later; both have an impatient rhythm. This is a retelling of tradition, not a conclusion from data — how to check it is described below.
What the checks showed
In 2007, sociologist David Voas (University of Manchester) compared the birthdays of spouses from the 2001 census of England and Wales — more than 10 million marriages. At first the data showed a small excess of same-sign couples, but Voas showed that it came from errors in how dates were recorded in the census; without them there are exactly as many matches as chance gives.
The limit of this check should be stated honestly: it only concerned Sun signs. Full charts of two people — with the Moon, Venus and Ascendant — have not been checked at such volumes. So the conclusion is narrow: the Sun sign alone does not predict who starts a family with whom.
What the sign can’t tell you
The Moon changes sign roughly every two and a half days, so for two Aries it can be in any of the 12 signs. Venus never moves more than 47° from the Sun, and for an Aries it can be in Aquarius, Pisces, Aries, Taurus or Gemini. The Ascendant depends on the hour of birth and can also be anything.
Synastry — reading a couple from two charts — compares exactly the Moon, Venus and Ascendant of the two people. So two Aries couples, one with Venus in Pisces and one with Venus in Gemini, read differently in it, even though their Sun sign is the same.
How to calculate your couple
On My Seven Charts (svoya-karta.ru), the couple calculation takes two dates of birth and compares them in four systems at once: natal chart aspects, Human Design, Jyotish kuta points and numerology numbers. The summary is free; the time and place of birth refine the result but are not required.
How to check it on yourself
Check it on your own couple — write down your answer before you look at the calculation.
Think of five couples you know where both are Aries (or your own couple, if you’re both Aries), and five other couples from your circle.
What should match. If tradition is right, in most couples of two Aries (at least 3 out of 5) the argument over who decides happens once a month or more often and started in the first months of knowing each other, while among other couples in your circle this is the case in fewer than half. Five couples is a small sample: it’s a pointer, not proof.
When it’s not about you. If couples of two Aries have no more such arguments than others, the description by sign doesn’t fit your circle. This agrees with the check of 10 million marriages.
Check the sign itself: open your natal chart and find where your Sun is.
What should match. An Aries has the Sun in Aries with a birthday roughly from March 21 to April 20.
When it’s not about you. If your birthday is March 19–21 or April 19–21, the Sun may have been in the neighboring sign — go by the exact date and time, not by a table from a magazine.
Calculate the couple from two dates and compare which signs your Moons are in.
What should match. By tradition, the “flare up and make up fast” description is stronger when both Moons are in fire signs (Aries, Leo, Sagittarius).
When it’s not about you. If both Moons are in earth or water, and you have shouting fights more often than once a month, the Moons don’t explain anything in your couple; neither does the Sun sign.
Why the house of the Sun gives away the time of birth and where to find true noon — on the page of all houses. How we check everything else — the site’s method.
The dates don’t go anywhere from here: the calculation happens on the compatibility page.
Frequently asked questions
Are two Aries a good match?
In astrological tradition — yes, as a couple of one element, but with a struggle over who leads. A check of 10 million marriages did not find that the Sun sign affects who marries whom, so it’s worth looking at the full charts of both people.
Why do two Aries have different compatibility?
The Sun sign is the same for everyone whose birthday falls in the Aries month. The Moon, Venus and Ascendant of two Aries can be in different signs — these are what astrologers compare in synastry.
How do I check Aries and Aries compatibility by date of birth?
Enter both dates in the couple calculation on My Seven Charts (mysevencharts.com/compatibility/). It compares natal charts, Human Design, Jyotish and numerology; the summary is free.
Who leads in a couple of two Aries?
By tradition, the one with the stronger Mars leads — in Aries, Scorpio or Capricorn. Check it on yourself: if decisions in your couple are more often made by the one whose Mars is in another sign, this sign doesn’t work for you.