What the synastry aspect grid shows
The synastry aspect grid is a matrix of every major aspect formed between two people's charts. Your planets, angles and sensitive points run down the side. The same set for your partner runs across the top. Wherever a row and column form a conjunction, sextile, square, trine or opposition within orb, the cell fills in.
The result is a single picture of how the two charts interlock. Instead of reading one aspect at a time, you can spot patterns — a whole busy column, or a quiet row — that a flat list hides.
How the grid is built
Each chart is cast independently with sub-arcsecond astronomy (VSOP87/ELP via astronomy-engine), using the Porphyry house system. Then, for each person, we gather a labelled set of points: the ten planets, the Ascendant and Midheaven, the North Node, Lilith, and the Part of Fortune. When a birth time is known we add the Vertex and Anti-Vertex too.
That gives up to seventeen points per chart. We then test every pairing across the two sets against one shared list of aspects and orbs. A cell can hold at most one aspect, the tightest that applies, so the grid stays clean. Cells are coloured by tone, with soft aspects in green and hard ones in red.
Reading across and down
Hover any cell to see the exact aspect and its orb. Scan a row to learn where one of your points is active in the other person's life. Scan a column to see which of your partner's points press on you the hardest.
For a quick start, look at the shortest list of contacts under the grid. That ranks the same cells by tightest orb, so you can read the strongest threads first and wander the matrix after. Try not to count filled cells as a score. A busy grid and a quiet grid can describe two very different relationships, and the meaning lives in which points talk to each other, not how many times they do.
What you get
After you cast both charts:
- A full A×B grid of cross-aspects, colour-coded soft or hard.
- A total count of how many contacts the two charts form.
- Row and column labels that name every point, so you always know which axis you are reading.
- The twelve tightest contacts listed as plain sentences.
- A clear note whenever an unknown birth time removed angle-based points.
A worked example
For two test charts, comparing only the ten planets produces twenty-four contacts. Once the grid also carries the angles, Node, Lilith, Fortune and Vertex, the same pair lights up seventy-four cells. Fifty of them live entirely in the extra rows and columns.
The single tightest contact in that test is a square between one person's Ascendant and the other's Moon, closing at just 0.0° of orb. A plain planet-only report never surfaces it, because the Ascendant is not a planet.
That is the value of the grid. The important synastry threads are often the ones a shorter list quietly omits.
How to weigh what you see
A crowded grid does not mean a good match, and a sparse one does not mean a poor one. Density says the two charts talk a lot. Quality — whether those conversations feel easy or effortful — depends on which planets and which aspects are involved.
Look for the personal points. A grid heavy with Moon, Venus and Mars contacts carries a different flavor than one dominated by outer-planet squares that everyone your partner's age shares. Angles like the Ascendant mark where the relationship plays out in daily life. Because the slow planets travel so little in a lifetime, many of their cells are shared with anyone born in the same window. The personal points carry the part of the weave that is specific to just the two of you.
Grid versus the classic synastry list
Both use exactly the same cross-aspect math and the same orbs. They are two views of one calculation. Our full synastry tool ranks the aspects and adds house overlays plus a compatibility score. This grid tool drops the score on purpose.
The point of a grid is to let you judge the whole pattern yourself, spatially, rather than being handed a number. If you want the ranked narrative and the score, use the synastry calculator. If you want to see the shape, use this one.
What this tool does not claim
The aspect pattern is real geometry, but its meaning is traditional symbolism rather than measurement. There is no evidence that aspect grids predict relationship outcomes. We treat the map as a prompt for reflection, never as a forecast.
Two practical notes. If a birth time is unknown, that person's Ascendant, Midheaven and Vertex are left out rather than guessed, so their rows and columns cover fewer points. And the grid lists contacts without judging which matter most; that weighing stays with you.
Our method in one line
Two independent natal charts (sub-arcsecond astronomy (VSOP87/ELP via astronomy-engine)), every labelled point of one swept against every labelled point of the other on a single shared aspect and orb table. Reviewed by Dr. Amara Osei, Astronomy Reviewer.
Step by step
- 1
Enter your birth details
Your date, time and place, used to cast your chart's points and angles.
- 2
Enter your partner's details
Their date, time and place in the second panel to build their side of the grid.
- 3
Build the aspect grid
The matrix fills in instantly, entirely in your browser, sorted by tightest orb.
- 4
Read the pattern, not just cells
Scan rows and columns for clusters.
Tip — The tightest-contacts list under the grid is a fast way in.
Frequently asked questions
- Does the grid give a compatibility score?
- No, and that is deliberate. A grid is meant to show you the whole pattern so you can weigh it yourself. If you want a banded score, our main synastry calculator offers one, always paired with the underlying aspect list so the number never stands alone.
- Why do some rows or columns look empty?
- An empty line means that particular point forms no major Ptolemaic aspect with any of the other person's points inside orb. Not every degree aspected every other degree, so gaps are normal and meaningful. A quiet row simply says that part of you stays unactivated by the pairing.
- What are the Vertex and Anti-Vertex doing in the grid?
- They are sensitive points on the eastern horizon where the ecliptic crosses the prime vertical. Modern astrologers read the Vertex as a fated-encounter marker, so we include it in the sweep. Both are time-based, so they only appear when a birth time is known.
- Do I need both birth times for the grid?
- You only need them for the angle and Vertex rows. The ten planets form their aspects from birth dates alone. Without a time, the tool drops the Ascendant, Midheaven, Vertex and Anti-Vertex and tells you it did, so the grid simply shrinks rather than showing anything invented.
- Is my birth data private?
- Calculations run entirely in your browser. Your birth data is never uploaded, never stored on a server, and never shared. The two charts, the point sweep and the whole grid are computed on your device, and nothing about either person is ever uploaded or stored.
Written by
Elena Marchetti
Founder & Staff Astrologer
Methodology reviewed by
Dr. Amara Osei
Astronomy Reviewer
Published 2026-10-03 · Updated 2026-10-03 · Calculated with sub-arcsecond astronomy (VSOP87/ELP via astronomy-engine)