Birth Charts Without a Known Birth Time
What you can discuss without a recorded time, what remains uncertain, and what to try instead.
Birth Chart Compatibility
Compare ten bodies at two known birth moments using dates, local times, and historical UTC offsets. See tropical zodiac positions and major aspects, without a love score.
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Your Planetary Comparison
These are calculated positions and angular relationships, not a measurement of love. Sign degrees are rounded; aspect matching uses unrounded positions.
Person 1
| Body | Sign | Within sign |
|---|
Person 2
| Body | Sign | Within sign |
|---|
Major aspects
A fixed 6° tolerance is used for conjunctions, sextiles, squares, trines, and oppositions. The closest matches appear first. More aspects do not mean greater compatibility.
No major aspects meet the chosen tolerance.
| Person 1 | Person 2 | Aspect | Separation | From exact |
|---|
How to compare two birth charts
For each person, enter a birth date, the recorded local birth time, and the UTC offset that applied at the birthplace on that date. Select Compare Planetary Positions to see the two position tables and the aspects between them. Use Clear Details to remove the inputs and results.
A UTC offset tells the calculator how the local clock differed from universal time. For example, 3:00 p.m. with an offset of -05:00 represents 8:00 p.m. UTC. Check the historical offset, including daylight saving time; your current time zone is not a substitute.
Use the full date and a 24-hour time: 7:30 p.m. is 19:30. Enter offsets with a sign and two-digit hours and minutes, such as -04:00 or +05:30. The tool accepts dates from 1900 onward and offsets from -12:00 to +14:00, and rejects future birth moments. Check these details before interpreting a table.
How to read the planetary comparison
Each position table lists a body, its tropical zodiac sign, and its degree within that sign. The aspect table compares a body from Person 1 with a body from Person 2. Separation is the smaller angle between their zodiac longitudes, from 0° to 180°; From exact shows how far that angle is from the named aspect.
The five major aspect angles are conjunction (0°), sextile (60°), square (90°), trine (120°), and opposition (180°). We allow a fixed 6° tolerance, called an orb. A 117° separation, for example, appears as a trine 3° from exact. The closest matches appear first; more rows do not mean a better relationship.
Read the degrees without adding a verdict
The sign gives a 30° section of the zodiac; the degree locates a body within it. For example, 5° Taurus corresponds to a longitude of 35° because Aries occupies the first 30°. A position can therefore move from late Aries to early Taurus without making a large jump around the circle.
Aspect matching uses unrounded positions, while the displayed values are rounded to two decimal places. Near the 6° cutoff, two rows that look nearly alike may fall on different sides of the rule. An empty aspect table means none of the included pairs met that rule; it is not an incompatible-couple verdict.
Calculation method and scope
We convert each local birth time using the offset you enter. Astronomy Engine 2.1.19 calculates positions relative to Earth's center, with aberration correction, in the true ecliptic of date. Longitudes are divided into twelve equal tropical zodiac signs. Every included body in one chart is compared with every included body in the other.
The calculator uses the locally bundled, MIT-licensed Astronomy Engine. Pluto is included as an astrology chart body. The fixed orb is our disclosed convention, not a universal standard. This limited comparison does not provide a full synastry interpretation or a relationship prediction. Our beginner's guide to synastry explains the terminology.
Birth chart compatibility questions
Can I use this without a birth time?
This tool requires a known time and historical UTC offset. It does not offer an unknown-time range, so do not enter noon just to complete the form. Read what an unknown birth time leaves uncertain, or try the zodiac sign calculator for a simpler game.
Why is there no birthplace field?
The positions are measured from Earth's center, so this version does not use geographic coordinates. You still need the birthplace's historical time-zone offset. Location-dependent houses, the Ascendant, and topocentric positions are outside its scope.
Will it tell me whether we are compatible?
It shows calculated positions and angular relationships. Those calculations do not establish that astrology can predict a couple's future. There is no overall love score, soulmate verdict, or best-match ranking.
Why might another chart site list a different aspect?
Compare the converted UTC moments, included bodies, zodiac system, and aspect tolerances first. A tool with different orbs or extra points can list different rows. The Sun sign and birth chart comparison guide helps distinguish a sign game from a planetary calculation.
Are my birth details sent anywhere?
The chart form calculates in your browser without submitting its birth fields to our calculation server or an external astrology API. It does not save a chart history. The website separately uses Google Analytics and Microsoft Clarity; the main calculator content is marked for masking in Clarity recordings. Read the privacy notice for analytics, sessions, and hosting details.