☾ Chandrabalam Calculator: Is the Moon With You Today?

Give your birth nakshatra, your Moon sign or your birth date, and where you are. Each row is one Vedic day, sunrise to sunrise, with the Moon's nakshatra and sign, the minute it changes, and the sum behind each answer.

Chandrabalam, the strength of the Moon, asks a simpler question than tarabalam: where is the Moon today, counted from where it was when you were born? You need only your birth Moon sign, the Janma Rashi. Count the signs from it to today's Moon sign, counting both ends, and the count is the house the Moon occupies from your Moon.

The Moon is read as favourable in the 1st, 3rd, 6th, 7th, 10th and 11th from your birth Moon, and unfavourable in the 2nd, 4th, 5th, 8th, 9th and 12th. This is the Moon's gochara, its transit from the natal Moon, applied to choosing a day. It is the version found in the standard Jyotish texts on transits (Brihat Parashara Hora Shastra, Phaladeepika) and in the muhurta almanacs built on them; Umbriel has followed the common almanac form and has not checked it verse by verse.

A common variant also tolerates the 2nd, 5th and 9th while the Moon is waxing (the bright half, Shukla paksha). Umbriel does not apply it, so a day it marks unfavourable may be acceptable under that rule. The calendar prints the position so you can apply either.

Suppose your birth Moon is in Gemini, sign 3, and the Moon is today in Virgo, sign 6. The count is 6 − 3 + 1 = 4: the Moon is in the 4th from your Moon, which is unfavourable. If it were in Scorpio, sign 8, the count would be 8 − 3 + 1 = 6, the 6th, favourable. If it were in Capricorn, sign 10, the count would be 10 − 3 + 1 = 8, the 8th, which is also Chandrashtama.

Each row of the calendar has that sum written out with your sign and the day's.

Most people know their Western, tropical Moon sign. Chandrabalam uses the sidereal sign, and the two differ by the ayanamsa, about 24 degrees at present. When the tropical Moon is in the first 24° of a sign, which is about four times in five, the sidereal Moon is in the sign before. Someone with a tropical Gemini Moon at 10° usually has a sidereal Taurus Moon. If you only know the Western sign, do not feed it in here: choose "I know my birth date" instead and let Umbriel work out the sidereal sign.

The Moon stays in a sign for about two and a quarter days, so on roughly four birth dates in nine it changed sign during the day. If you give a date and no time, Umbriel lists the signs the Moon was in that day with the times, and shows every possibility in the calendar. Where two possible birth signs would give different Chandrabalam on a given day, the row says "depends on birth time" and gives both, rather than picking the pleasant one.

The Moon comes from the same engine that casts every chart on Umbriel, in the sidereal zodiac with the Lahiri ayanamsa. The calendar finds each moment the Moon crosses a nakshatra boundary (every 13°20′) or a sign boundary (every 30°) by stepping through the month two hours at a time and then halving the interval until the crossing is pinned to a fraction of a second. Sunrise is the Sun's upper edge at the horizon for the place you choose, the Vedic day's own starting line, so each day runs from one sunrise to the next. The classification is then pure counting, and the sum is printed under every answer. Nothing is sent anywhere: the page works in your browser, and the calculation engine (about 780 KB) is only fetched when you first touch the form.

Checked, not assumed. The engine's Moon was compared with NASA JPL Horizons (apparent longitude of date, the geocentre) at 80 instants spread from 1950 to 2161. For the 66 of them up to the end of 2027 the largest difference was 0.17 arcminute (0.07 on average), about twenty seconds of the Moon's travel; the engine drifts to a few arcminutes by the 2100s, so only dates in the next few decades are this exact. Against a published online panchang (Drik Panchang) on five days in five places (New Delhi, Mumbai, Chennai, Kolkata and New York, between October 2026 and March 2027) every nakshatra and Moon-sign change time agreed to within one minute, and our sunrise came 1 to 1.5 minutes earlier than theirs. Not checked: the classical verse for each convention below (see the questions), birth times from before 1970 (the zone rules come from your browser, and old daylight-saving rules are the likeliest thing to be wrong), and anything beyond 30 days ahead, which the calendar does not offer.

Chandrabalam is one input to a muhurta, not a forecast. The calendar does not weigh the tithi, weekday, yoga or the planets that the full craft weighs, and it makes no claim that a favourable Moon changes how a day goes.