Attraction
Compare a stated pair of placements or aspects. Do not turn one contact into a prediction of duration.
Keep three questions from becoming one claim
Compatibility
Describe where two chart placements can be compared; it is not a measurement of someone’s worth or suitability.
Timing
A dated transit is a separate calculation. Do not quietly add it to either person’s natal chart.
This page’s original contribution is the three-question record: every observation should carry a label—attraction, compatibility or timing—before it carries an interpretation. That prevents a transit, a natal aspect and a preference from being presented as the same evidence.
A small comparison protocol
Check both source records
Save each date, time, place, zodiac setting and house system separately. An unknown birth time leaves houses and angles unresolved for that person.
Choose one pair to inspect
For example, write the two planets, their displayed positions and the aspect rule. Avoid a long list of labels with no declared question.
Read the contact in its category
Call a natal-to-natal comparison a chart comparison. Call a date-specific transit a timing observation. Keep the labels distinct.
One useful saved line: “Question: [category]. Chart A setting: [setting]. Chart B setting: [setting]. Compared pair: [two positions].” A result someone else cannot reconstruct is not a useful calculator output.
What a calculator should not decide for you
A chart comparison cannot establish consent, communication, safety, commitment or whether a relationship is good for either person. Those are lived decisions. The calculation can be a reflection prompt only after its inputs and scope are clear.
For a single relationship chart created from midpoints, use the composite chart guide; it answers a different calculation question from comparing two natal charts.
Synastry chart calculator questions
Do I need two exact birth times?
Exact times make angle and house comparisons more dependable. Without them, keep time-sensitive claims unresolved rather than guessing an Ascendant.
Is synastry the same as a composite chart?
No. Synastry compares two natal charts; a composite chart uses a separate midpoint construction.
Can a calculator predict whether we will stay together?
No. A calculation can describe a selected chart relationship under stated rules, not make a reliable forecast or decision for you.
What should I save?
Save both input records, settings, the named comparison pair and the exact question. See the related star chart calculation guide for a single-chart reading order.