Comparing two charts fairly
Comparing two charts fairly means using the same settings for both: the same ayanamsa, the same house system, and the same reference for the Moon sign and nakshatra.
What it is
Enter both sets of birth details carefully, note the time zone for each, and read each chart on its own before comparing. Compare the Moon signs, the Lagna signs and the lords of the houses of interest.
How it is worked out or read
The site shows each chart separately and does not combine them. A written comparison, with the settings noted, is the most reliable record.
Where it appears on this site
See mutual compatibility principles and matching limits.
Start with the same settings
Before comparing two charts, make sure they were made the same way. Both should use the same ayanamsa, the same house system and the same chart style. A comparison between a Lahiri chart from one source and a Raman chart from another can show differences that come only from the settings, not from the people. The simplest approach is to recalculate both charts on the same calculator, which this site lets you do in two browser tabs or two printed pages side by side.
Also note how reliable each birth time is. If one time is a rough estimate, any comparison that depends on the Lagna or the houses should be held more loosely than one that depends on the Moon's sign.
Compare the Moon first
In Jyotish the Moon is the usual starting point for comparing two people. Write down each person's Moon sign and nakshatra. The relationship between the two Moon signs, counted from one to the other, is the basis of bhakoot in matching, and the two nakshatras are the basis of tara, yoni, gana and nadi. Even outside a marriage context, the Moon comparison gives a quick picture of how two temperaments may meet.
The articles on each kuta on this site explain how these comparisons are scored, so that a reader can work them out by hand.
Then the Lagna and the houses
Next, see where each person's Lagna falls in the other's chart. If one person's Lagna sign is the other's seventh house, for example, the tradition reads a natural link of partnership. Then look at where the key grahas of one chart fall in the houses of the other: one person's Moon in the other's fourth house or Venus in the other's seventh are the kind of overlays readers note. This method is less formal than Ashtakoota, and different readers weight it differently, but it can add useful detail.
Timing side by side
A comparison is not only about the charts at birth. Lay out the dasha periods of both people for the same years. Two people in demanding periods at the same time may need more patience with each other, while periods that support each other can mark good years for shared plans. The dasha tool on this site can be run for each person, printed, and laid side by side for this purpose.
A caution on conclusions
Comparing charts is a way to describe tendencies, not to decide whether a relationship, partnership or family bond is good or bad. People with very different charts often get along well, and people with matching charts still need to work at their relationships. Use the comparison to start a thoughtful conversation, and keep decisions with the people involved.