Moon Phase Calculator
The Moon’s phase comes from the angular gap between the Sun and the Moon. At 0° it is Amavasya, at 180° Purnima — and a tithi is each 12° step of that same gap.
What this calculator tells you
This gives the Moon’s phase for any date — new moon, full moon or anything between — along with the illumination percentage, the tithi, the Moon’s sign and its nakshatra.
How the calculation works
The phase comes from the angular difference between the Sun and the Moon. At 0° it is the new moon, at 180° the full moon. The illumination follows from the same difference. So does the tithi, which is that difference divided into 12° steps — which is why phase and tithi always move together rather than being two separate things.
How to read the result
Illumination and tithi check each other: at the full moon illumination should be near 100%. One point is often misunderstood — the phase is identical worldwide at any given instant. Unlike sunrise, it does not vary with location. Only the calendar date can differ, because the day begins at different moments in different places.
Common questions
How does the tithi differ from the phase?
Not in what is measured, but in how it is expressed. Both come from the same difference — the phase states it in degrees, the tithi in thirty steps of 12°.
Why is no birth place asked for?
Because the phase does not depend on location. That is a fact of astronomy, not a limitation of this calculator.
Should I use this to fix a vrat date?
For a vrat, use a local panchang — there the tithi is counted from sunrise, which does vary by place. This page gives the phase, not a ritual decision.