How the moon phase is calculated

The Moon has no light of its own — what we call its phase is simply how much of its sunlit half faces Earth. This page calculates the angle between the Sun and the Moon as seen from Earth (the geocentric elongation) for the current moment. An angle of 0° is a New Moon, 90° is the First Quarter, 180° is a Full Moon, and 270° is the Last Quarter; everything in between is a waxing or waning crescent or gibbous phase. The illumination percentage shown above comes directly from that angle.

Alongside the phase, the page shows which zodiac sign the Moon currently occupies — using the Lahiri sidereal zodiac, the star-based reference frame of Vedic astrology. Sidereal positions run about 24 degrees behind the tropical zodiac used on most Western websites, so if your Moon sign here differs from what another site says, that offset is the reason, not an error.

The waxing half of the cycle (New Moon to Full Moon) is traditionally the building phase — favourable for starting projects, growing efforts, and initiating conversations. The waning half (Full Moon back to New Moon) favours completing, reviewing, releasing, and rest. For example, if today shows a Waxing Gibbous at 80% illumination, you are in the final push before a Full Moon — in Vedic timing, a period suited to finishing what you started rather than opening a new front.

The lunar phase is global: everyone on Earth sees the same phase on the same night, so it describes the sky, not you. Which house of your chart a particular Full Moon lands in, and whether it touches anything personal, takes your birth details — that mapping is what the Vedara app does.

Frequently asked questions

What moon phase is it tonight?

The top of this page shows the current phase, its illumination percentage, and the Moon’s sidereal zodiac sign, calculated live from the geocentric Sun–Moon angle. It updates continuously, so the answer is always for right now.

Why is my Moon sign different from other astrology sites?

Vedara uses the Lahiri sidereal zodiac, the standard in Vedic astrology, which is offset roughly 24 degrees from the tropical zodiac used by most Western sites. The Moon’s physical position is the same — the two systems just label it against different reference points.

How long does each moon phase last?

The full lunar cycle takes about 29.5 days. The four principal phases — New Moon, First Quarter, Full Moon, and Last Quarter — are exact moments, while the crescent and gibbous phases between them each span roughly a week.

What does the Full Moon mean in Vedic astrology?

Purnima, the Full Moon, is considered the peak of the lunar cycle — a culmination point when efforts begun at the New Moon come to light. Its personal effect depends on which house and nakshatra it falls in relative to your own birth chart.

Related tools

• Today’s Nakshatra — which lunar mansion the Moon occupies right now
• Planetary Hours — which planet rules this hour at your location
• Daily Timing — today’s overall energy score from live planetary positions