How accurate is this?

The underlying angle calculation is accurate to a small fraction of a degree, which translates to a few minutes of real time. The one remaining limitation is that this tool only takes a date, not a time — so right at a phase boundary, the true local phase can differ by a few hours from what midday UTC shows.

What's the difference between Moon phase and tithi?

Moon phase (new/full/etc.) is a simpler 8-way division most people know; tithi is a finer, 30-part classical Vedic measure of the same Moon-Sun angle, used in panchang and computed by the same engine that builds your birth chart.

Can I check a past or future date?

Yes — enter any date and the calculator computes that date's Moon phase.

Moon Phase Calculator

चंद्र कला कैलकुलेटर

What phase was the Moon in on a given date?

Enter any date to see the Moon's phase — new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, last quarter, or waning crescent — and its illuminated percentage, calculated from the actual Sun-Moon angle in the sky (not a calendar-arithmetic guess), accurate to within a few minutes.

A real calculation, not a calendar guess

This calculator computes the Sun's and Moon's actual position in the sky (their ecliptic longitudes, via the standard formulas from Jean Meeus's Astronomical Algorithms) and takes the angle between them — that angle alone determines both the phase name and how much of the Moon is lit. It runs entirely in your browser, with no server round-trip, so it stays instant while still being a real astronomical calculation rather than a rough date-based approximation.

Common questions

How accurate is this?: The underlying angle calculation is accurate to a small fraction of a degree, which translates to a few minutes of real time. The one remaining limitation is that this tool only takes a date, not a time — so right at a phase boundary, the true local phase can differ by a few hours from what midday UTC shows.
What's the difference between Moon phase and tithi?: Moon phase (new/full/etc.) is a simpler 8-way division most people know; tithi is a finer, 30-part classical Vedic measure of the same Moon-Sun angle, used in panchang and computed by the same engine that builds your birth chart.
Can I check a past or future date?: Yes — enter any date and the calculator computes that date's Moon phase.