The moon's orbit around Earth isn't a perfect circle — it's a slight ellipse, meaning the moon's distance from Earth varies over each orbit. A "supermoon" is an informal term (not an official astronomical one) for a full moon that occurs at or near perigee, the closest point in that orbit.
How much bigger does it actually look?
A supermoon can appear up to about 14% larger in diameter and up to about 30% brighter than a "micromoon" (a full moon at apogee, the farthest point in the orbit). In practice, because the difference happens gradually and there's nothing nearby in the sky to compare it to, most people can't reliably tell a supermoon apart from an ordinary full moon just by looking — it's a real, measurable effect but a subtle one to the naked eye.
The moon illusion
Separately from actual supermoons, a full moon near the horizon often looks dramatically larger than one high in the sky — this is the "moon illusion," a perceptual effect related to how the brain judges size relative to foreground objects like trees or buildings, not an actual change in the moon's distance. It happens on any full moon, super or not.
When's the next one?
Supermoons cluster around a few full moons each year, typically in the months closest to the moon's most extreme perigees. Check the 2026 full moon calendar for specific dates, and the homepage for the current phase.