Composite Chart Calculator
Generate precise composite charts that blend two birth charts into a unified relationship map, revealing the unique energetic signature of your partnership through midpoint calculations of planetary positions and house cusps.


How to use Composite Chart Calculator
Steps to get you started in BasedLabs.

Step 1
Enter Both Birth Details
Input complete natal data
Enter precise birth information for both individuals including date, exact time, and geographic location. Ensure birth times are as accurate as possible since even 10-minute discrepancies can shift house cusps by 2-3 degrees. The calculator uses these coordinates to determine planetary positions in the zodiac and calculate accurate midpoints for all chart elements including the Ascendant, Midheaven, and nodal axis.

Step 2
Review Calculated Midpoints
Analyze planetary positions
Examine the composite planetary placements generated through midpoint calculations, paying special attention to the composite Sun (relationship identity), Moon (emotional foundation), and Venus (affection style). Note any composite planets in angular houses (1st, 4th, 7th, 10th) which indicate emphasized relationship themes, and identify major aspect patterns like T-squares, grand trines, or stelliums that shape relationship dynamics.

Step 3
Interpret Relationship Patterns
Decode composite aspects
Study the aspect grid to understand how composite planets interact, focusing on tight aspects within 3-degree orbs for strongest influence. Challenging aspects like composite Saturn square Venus reveal growth areas requiring conscious work, while harmonious aspects like composite Jupiter trine Mercury indicate natural strengths. Consider house placements alongside aspects—a composite Moon in the 8th house with hard aspects suggests intense emotional bonding with transformative challenges.
Precise Midpoint Methodology
Our calculator employs rigorous midpoint mathematics including shortest-arc calculations to ensure planetary midpoints never exceed 180 degrees of separation. The system automatically handles special cases like Mercury and Venus composites that require careful consideration of zodiacal proximity, and accurately calculates derived angles including the composite Ascendant and Midheaven using sophisticated geodetic algorithms trusted by professional astrologers.

Complete Aspect Pattern Recognition
Automatically detects and highlights significant aspect patterns including T-squares, grand crosses, grand trines, yods, and stelliums within your composite chart. The system calculates aspects using professional orbs (8° for major aspects, 3° for minor) and color-codes aspect types for instant pattern recognition, allowing you to quickly identify the relationship's core geometric signatures that indicate karmic themes, creative potential, or inherent tensions.

Multi-House System Support
Generate composite charts using multiple house systems including Placidus, Koch, Equal House, Whole Sign, and Campanus to explore different interpretive layers of your relationship. Each house system emphasizes different dimensions—Placidus for psychological depth, Whole Sign for traditional interpretation, and Equal House for balanced life area analysis—giving you comprehensive perspectives on how your partnership manifests across various life domains.

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