Free tool · Moon phase
Moon Phase Calculator: any date, exact.
The Moon's phase for any date from 1900 to 2100: phase name, percentage illuminated, the Sun–Moon angle, the Moon's zodiac sign and degree, and the dates of the next new and full Moon. Today's figures come from the Shymea engine's live sky; other dates are computed in your browser from the same tropical geometry.
Full method, orbs and ephemeris on the methodology page.
The phase is the angle between the Sun and Moon seen from Earth. At 0° the Moon is new; at 180° it is full. Illumination follows that angle directly, so a first-quarter Moon is exactly half lit and a 45° crescent is about 15% lit.
The Moon's sign is a separate fact from its phase: a full Moon can fall in any of the twelve signs, always opposite the Sun's. The tool shows both so the two are not confused.
How this is calculated
Geocentric tropical longitudes of the Sun and Moon are taken for the date (noon UTC for past and future dates; the current instant for today). The phase angle is Moon minus Sun, illumination is (1 − cos angle) ÷ 2, and the eight phase names are 45° bands centred on the four principal phases. The next new and full Moon are found by scanning forward for the 0° and 180° crossings and refining to the minute.
Today's values are read from the engine's precomputed lunar table, which is the same number the app shows. Other dates use astronomy-engine in the browser, which agrees with the JPL ephemeris to well under a degree for the Moon.
Common questions
- Why does the phase differ slightly from another site?
- Most differences are the time of day. The Moon moves about 12° a day, so a phase quoted for midnight local time and one quoted for noon UTC can differ by a few percent of illumination.
- Is the Moon sign the same everywhere?
- Yes. The Moon's zodiac longitude is geocentric and does not depend on where you stand. Only the local clock time of a sign change differs.
- What are the eight phases?
- New, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, last quarter and waning crescent. Each covers 45° of the Sun–Moon angle, centred on 0°, 90°, 180° and 270° for the four principal phases.
Embed this tool on your site
Free for any website or newsletter. Paste the snippet where you want the widget; it computes in the reader’s browser and needs no account or API key. Add ?theme=dark or ?theme=autoto the URL to match your page. The only condition is that the credit line below the widget stays as it is.
<div style="max-width:420px">
<iframe src="https://www.shymea.com/embed/moon-phase" title="Moon phase today — Shymea" width="100%" height="210" style="border:0;display:block" loading="lazy"></iframe>
<p style="margin:6px 0 0;font:12px/1.4 system-ui,sans-serif">
<a href="https://www.shymea.com/tools/moon-phase-calculator/">Moon phase data by Shymea</a>
</p>
</div>More embeds, a live preview and install notes for WordPress and Squarespace are on the free widgets page.
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Positions are computed from the JPL DE442 ephemeris in the Tropical zodiac with Placidus houses. Readings are educational, drafted from the computed factors and edited by the Shymea team; they are not the work of a named practising astrologer and are not medical, legal or financial advice. See the editorial policy.