What progressed synastry is
Synastry overlays two natal charts and reads the aspects between them — a static photograph of a pairing. Progressed synastry keeps one half of the pair still: your progressed chart (your own birth chart advanced day-per-year to today) aspects your partner's unchanging natal chart, and vice versa. It is a moving photograph with two exposures, which is why it answers a different question: not 'do we match' but 'what is this pairing being fed, right now, by each person's own development?'
The convention behind it is the secondary progression: one sidereal day of planetary motion equals one year of life. The progressed Sun ambles about one degree every hundred months — a sign change is a decade-scale event — while the progressed Moon moves roughly 12–15° a year, hitting a new sign and a new aspect-to-your-partner every two and a half years or so.
How we compute it
Both natal charts are cast with sub-arcsecond astronomy (VSOP87/ELP via astronomy-engine). Each chart is then progressed to today: the elapsed years of life are converted to days at the one-day-per-year rate and the slow bodies' longitudes solved on that progressed date; the progressed Moon uses its true daily motion. The two progressed position sets are aspect-checked against the other partner's natal placements — tightest orbs first — in both directions, so the reading stays deliberately asymmetric.
The two directions are kept apart on purpose. Your progressed chart touching your partner's natal chart is not the same statement as theirs touching yours: the first is what your own maturation is currently bringing into the pairing, the second is what their development is bringing to you. Collapsing them into one symmetric list, as some services do, throws away the technique's main insight.
What you get
After entering two birth records, the report shows:
- Where each person's progressed Sun and Moon have grown to, beside where they were born — the decade-beat and the 27-year beat of each partner.
- Your moving chart → their natal chart: the strongest progressed-to-natal contacts of today, with exact orbs.
- Their moving chart → your natal chart: the same scan run in the other direction.
- A one-line reading per contact pairing the progressed body's theme 'as it has grown' with the natal body's theme 'as it arrived'.
Reading the moving axis
Practitioners treat progressed-to-natal synastry as the relationship's weather forecast layered on its climate. The progressed Sun crossing a partner's natal Saturn — the pairing's commitment point — is the classic example: as one person's core purpose literally matures into a new decade of its cycle, the relationship's structure is the sky it shows up under. A progressed Moon hitting a natal body is shorter but sharper: about two and a half years of mood, memory and nourishment tinted by whatever that natal planet governs.
The technique's quiet strength is that it explains sameness-with-shift: nothing about either person's birth chart has changed, no new transit storm is overhead, and yet the pairing demonstrably feels different. Progression says the individuals are moving — so the contact points between them move too.
A worked example: b. 1 Jan 1990 London with b. 15 May 1992 London, seen in October 2026
Take the first partner, 36.75 years old in October 2026: their natal Sun in Capricorn has progressed into Aquarius, standing at 18.2° — and it sits within 0.15° of exact conjunction to the second partner's natal Saturn. That is textbook progressed-synastry material: a once-in-a-lifetime meeting of one person's decade-scale purpose with the other's architecture of commitment, arriving neither at the start of the pairing nor by any transit of the shared sky, but simply because one chart has been walking toward that degree for 36 years.
The same scan fills in the smaller weather: the older partner's progressed Pluto sextile the younger's natal Uranus within 0.0°, progressed Uranus trine natal Mercury within 0.4° — 42 progressed-to-natal contacts in that direction alone, tightest first.
Run the other way, the younger partner's 34-year clock is busy on the older's chart too: progressed Mercury trine the older's natal Pluto within 0.1°, progressed Mars sextile the older's natal Moon within 0.2°. Two people, two clocks, one pairing — and a completely different aspect picture from the one their two natal charts alone would show.
What this tool does not claim
Secondary progression is a traditional convention, not astronomy: there is no physical reason the sky of the day after your birth should map to a year of your life, and no controlled evidence that progressions predict anything. What the engine computes exactly — planetary longitudes on progressed dates, real orbs between two people's positions — is real ephemeris math wrapped around an inherited timing device.
Orbs here are the site's standard aspect bands; progressed orbs tighten and part over months, so a 0.4° contact matters for roughly a year and a 2° one spans several. The two charts' birth times genuinely matter (progression rates are computed from the elapsed years, and an unknown time mainly softens the house context). All computation runs locally; your and your partner's birth data never leave your browser.
Where it sits next to other readings
The Synastry Chart answers the static question — how the two natal charts interlock at birth. The Composite & Davison Chart merges the pair into one chart of the relationship itself. Synastry Transit brings today's real sky to the pairing. Progressed synastry is the fourth angle: neither partner's sky nor the world's, but each person's own slow inner clock read against the other. Used together, the four cover climate, weather and growth on all sides of a relationship.
Our method in one line
Both natal charts cast from sub-arcsecond astronomy (VSOP87/ELP via astronomy-engine), each progressed day-per-year to the current date, and the two progressed position sets cross-aspected against the other's natal placements in both directions, sorted by exact orb. Reviewed by Dr. Amara Osei, Astronomy Reviewer.
Step by step
- 1
Enter both birth records
Date, time and place for each partner. Names are optional but label the two columns.
- 2
Progress the pairing to today
Each chart advances at one day per year of life — no data leaves your device.
- 3
Read your direction first
Your progressed bodies touching their natal ones: what your own development is currently bringing into the pairing.
- 4
Then read theirs
Tip: watch the progressed Sun and Moon — the Sun marks decade-turns, the Moon marks the current two-and-a-half-year mood. Tip: compare with the static Synastry Chart to see what has changed since the beginning.
Frequently asked questions
- How is this different from ordinary synastry?
- Ordinary synastry compares two frozen natal charts — the pairing's permanent climate. This tool advances each chart along its owner's life first (one day of ephemeris per year), so the aspects it finds are the ones that are live at your current ages. Contacts that were absent at the start of a relationship can appear, and long-standing ones can loosen, without either person's birth chart or the real sky doing anything new.
- Why are the two directions listed separately?
- Because they mean different things. Your progressed chart to their natal chart describes what your own maturation is currently activating in them; their progressed chart to your natal chart describes what their development is currently activating in you. The lists are genuinely not mirror images — in the worked example the two partners light up different bodies — and averaging them would erase that.
- What is the progressed Moon and why does everyone talk about it?
- The Moon moves about 13° a day in real sky, so day-per-year makes it crawl roughly 1° per three weeks of life and circle the zodiac once in about 27½ years. It therefore crosses every partner's natal point about monthly-to-yearly and changes 'sign' every two and a half years — the most eventful hand in the deck. Its natal sign and degree are the only inputs your birth date needs to fix it.
- Do we need exact birth times?
- For the aspect lists themselves, progressions depend only on the elapsed years and the natal planetary longitudes, so approximate times barely hurt. What softens without exact times is the house context — which field of each partner's life the contact plays in — and the progressed Ascendant and MC, which move a degree per four years and can shift sign with a wrong time.
- Is either of our birth data sent anywhere?
- Calculations run entirely in your browser. Your birth data is never uploaded, never stored on a server, and never shared. Both natal charts, both progressed charts and every cross-aspect are computed locally in your browser; nothing is uploaded or stored.
Written by
Elena Marchetti
Founder & Staff Astrologer
Methodology reviewed by
Dr. Amara Osei
Astronomy Reviewer
Published 2026-10-01 · Updated 2026-10-01 · Calculated with sub-arcsecond astronomy (VSOP87/ELP via astronomy-engine)