Antardasha Explained: How the Sub-Periods Are Calculated

One formula, and it never changes

The mahadasha tells you the theme of the era. The antardasha tells you what is happening this year, and it is the level most readings actually run on.

Every mahadasha contains nine antardashas, one for each planet, running in the standard Vimshottari order (Ketu, Venus, Sun, Moon, Mars, Rahu, Jupiter, Saturn, Mercury) but starting from the mahadasha lord itself. So a Saturn mahadasha opens with Saturn-Saturn, then Saturn-Mercury, then Saturn-Ketu, and so on around the cycle.

The length of each is fixed by a single formula:

antardasha years = (mahadasha years x sub-lord years) / 120

That is the whole thing. Because the 120 is constant, each sub-lord always takes the same percentage of any mahadasha it appears in. A Rahu antardasha is 15% of a Saturn mahadasha, 15% of a Moon mahadasha, and 15% of any other. Only the absolute length changes.

The one table you need

The table below is the useful form of that formula. It gives each sub-lord's fixed share, so you can work out any antardasha in any mahadasha with one multiplication rather than looking up a nine-by-nine grid.

To use it: take the length of the mahadasha you are in, multiply by the percentage, and you have the antardasha length. A Mercury antardasha inside a 19-year Saturn mahadasha is 14.167% of 19 years, which is about 2 years 8 months. The same Mercury antardasha inside a 6-year Sun mahadasha is 14.167% of 6 years, which is about 10 months.

The percentages sum to exactly 100, which is a useful check: if your software gives you nine sub-periods that do not add up to the parent, something is wrong.

The same logic goes a level deeper. Pratyantardasha, the third level, divides each antardasha by the same proportions again. The formula becomes mahadasha years multiplied by sub-lord years multiplied by sub-sub-lord years, divided by 120 twice. Most practical work stops at the second or third level, though the system continues to five.

How to read the pairing

The two lords are read together, and the relationship between them matters as much as either one alone.

The mahadasha lord sets the subject. The antardasha lord decides how that subject behaves this year. A supportive pairing, where the two planets are friends, sit in good houses from each other, or both are dignified, tends to produce the smoother version of the period. A hostile pairing produces friction even inside a broadly favourable mahadasha, which is why a good decade still contains bad years.

The practical shortcut most astrologers use: look at which houses the antardasha lord owns and occupies, counted both from the ascendant and from the mahadasha lord. That tells you which areas of life the year is likely to activate. A Venus antardasha where Venus rules your 7th will push relationships whatever the mahadasha is doing.

This is also why the opening sub-period of any mahadasha is distinctive. Saturn-Saturn, Venus-Venus, Jupiter-Jupiter and so on are the purest expression of that planet, undiluted, and they tend to set the tone people remember for the whole era.

Why your dates might not match another site's

Two sites can agree on your mahadasha and disagree on the antardasha dates, and the reason is almost always birth time.

The entire Vimshottari sequence is anchored to the Moon's exact position within its nakshatra at birth. The Moon moves about 0.549 degrees an hour and a nakshatra spans 13 degrees 20 minutes, so an hour of error shifts everything by about 4.12%. On a 20-year Venus mahadasha that is close to ten months, and every antardasha inside it moves by the same proportion.

So if your dates are out by months rather than days, check the birth time before you blame the software. If they are out by hours or a day, the ayanamsha setting is the more likely cause.

The other thing worth knowing: the mahadasha you were born into is usually already partly elapsed, since the Moon was somewhere in the middle of a nakshatra rather than at its start. Your first mahadasha is a remainder, not a full period, and its antardashas are counted forward from wherever that remainder begins.