Free Online Lunar Eclipse Calculator
Find lunar eclipse dates, type, duration, and visibility.
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Next lunar eclipse
Lunar eclipses are visible from the entire night side of Earth, so location matters less than for solar eclipses. The Moon must simply be above your horizon during the event.
Upcoming lunar eclipses
| Peak date | Type | Umbral obscuration | Penumbral | Partial | Total | Moon altitude |
|---|---|---|---|---|---|---|
| Search for an eclipse to populate this table. | ||||||
Durations describe the full phase, calculated as twice the semi-duration reported by the library. “Moon altitude” is evaluated at the peak time for the optional location.
About the Lunar Eclipse Calculator
A lunar eclipse occurs when the Moon passes through Earth's shadow. Unlike a solar eclipse, which can be seen only along a narrow track, a lunar eclipse is visible from anywhere on the night side of Earth where the Moon is above the horizon. The event unfolds slowly, often over several hours, and requires no special equipment. This calculator finds upcoming eclipses, classifies them by how deeply the Moon enters Earth's shadow, and reports peak dates, phase durations, and optional local visibility.
Penumbral, partial, and total eclipses
Earth's shadow has two parts. The outer penumbra receives some direct sunlight, so a penumbral eclipse produces only a subtle darkening that is often difficult to notice. The inner umbra is fully shaded. A partial lunar eclipse occurs when part of the Moon enters the umbra, creating a visible dark bite. A total lunar eclipse occurs when the entire Moon is inside the umbra. Even then the Moon rarely disappears: sunlight refracted through Earth's atmosphere bathes it in copper, orange, or deep red tones. The exact colour depends on dust, volcanic aerosols, and cloud cover along the day-night boundary.
Understanding the numbers
Umbral obscuration is the fraction of the Moon's apparent disc covered by the umbra at maximum eclipse. It is zero during a purely penumbral event, between zero and one during a partial eclipse, and exactly one for a total eclipse. Durations are given separately for each stage. The penumbral duration is always the longest, the partial duration begins when the Moon first touches the umbra, and the total duration applies only when the umbra covers the whole disc. A total eclipse can remain in totality for anywhere from a few minutes to more than an hour and a half.
Why the Moon turns red
During totality, the only sunlight reaching the Moon has travelled through Earth's atmosphere. Air molecules scatter short blue wavelengths much more strongly than long red wavelengths, a process called Rayleigh scattering. The light that survives the journey is therefore reddened, and it is bent into the shadow by refraction. This is the same optical effect that colours sunsets. A lunar eclipse is effectively a projection of every sunrise and sunset on Earth onto the lunar surface at once.
Observing tips
- No filter is needed; lunar eclipses are safe to watch with the unaided eye, binoculars, or a telescope.
- Find a location with an unobstructed view toward the Moon during the event.
- Photography exposures lengthen dramatically during totality, so use a tripod and experiment with several shutter speeds.
- Penumbral shading is easiest to see in photographs or by comparing the Moon with nearby stars.
- Check the Moon altitude column to confirm that the event is above your horizon.
Frequently asked questions
Why is the Moon altitude sometimes negative?
A negative altitude means the Moon is below the horizon at the eclipse peak from the selected coordinates. The eclipse still happens, but it cannot be observed from that location at that moment.
Does every full moon produce a lunar eclipse?
No. The Moon's orbit is inclined, so most full moons pass above or below Earth's shadow. An eclipse requires the full moon to occur close to an orbital node, which happens only a few times per year at most.
How long does a lunar eclipse last?
A penumbral phase can last more than five hours, while totality usually lasts between 30 minutes and 1 hour 45 minutes. The entire visible event from first penumbral contact to last contact can exceed six hours.