What this calculator tells you
Your Mars sign comes from Mars’s geocentric ecliptic longitude at birth. The calculator shows that sign and degree together with a house and motion label. These measured fields provide a starting point for interpretation without turning symbolic meanings into factual predictions.
What the Mars result contains
Read the position first, then the house and motion. The sign divides the zodiac into twelve 30° sectors. The house locates Mars inside the time-and-place-dependent chart. Direct or retrograde describes how its apparent longitude is changing at the birth instant.
The current runtime uses the JPL Mars-system barycentre convention recorded in its calculation provenance. That astronomical definition is separate from astrology’s symbolic use of Mars. Keep source conventions aligned if comparing very small numerical differences between engines.
Inspect Mars’s aspects instead of guessing from signs
Two planets in signs traditionally described as square are not necessarily within your chosen square orb. Exact longitude separation decides which aspects the tool returns. Open the aspect list to see the angle, actual orb and allowed orb.
Traditional readings often associate Mars with action, assertion or conflict. A placement does not establish a person’s aggression, health or future behaviour. Use the calculated chart as context for symbolic reflection, not as a diagnosis.
A CONCRETE EXAMPLE
Mars in the fixed Greenwich example
The fixed example has Mars at 27°58′ Aquarius in House 11. It is late in Aquarius, but still inside that sign; a degree close to 30° is not rounded into Pisces when determining the sign. The original unrounded longitude defines the sector.
This preserved, fictional example uses 1 January 2000, 12:00 UTC, Greenwich (51.4779° N, 0°), tropical zodiac and Alcabitius houses. Its stored source is Swiss Ephemeris 2.10.03. New calculations use Skyfield + JPL DE440; the historical example is not relabelled as a new calculation.
Read it in your own chart.
Keep the date, recorded time, location and zodiac visible as you compare results. Guest calculations need no account.
Use the calculator aboveCommon questions
Does Mars near 30° belong to two signs?
The calculation assigns one sign from the unrounded longitude. A position may be close to a boundary, but that proximity does not make it occupy both sectors. Check uncertain birth times separately.
Can I calculate today’s Mars sign here?
This page focuses on natal Mars. Use Current planetary positions for Mars at the present instant, or Daily ephemeris for daily samples in a chosen month.
Why did the house change when I changed the settings?
House systems divide the chart differently. Mars’s zodiac longitude can remain the same while a different cusp structure gives a different house number.
Calculation & interpretation
New personal calculations use Skyfield with JPL DE440 data and the site’s documented house and zodiac rules. The preserved Greenwich teaching chart has its own historical source label. Worked arithmetic and geometry examples are labelled separately. Astrological meanings are symbolic conventions, not established scientific predictions.
Birth time and place affect angles and houses. Unsupported or ambiguous inputs return an error rather than an invented chart. Personal results stay in browser state and do not create public result URLs.
- Skyfield: positions and coordinates
- NASA/JPL: planetary and lunar ephemerides
- IANA: time zone database