Next Full Moon Calculator
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Count down to the next full moon from any start date — calendar date and days until.
Start date
Next full moon
2026-08-28
21 days after 2026-08-07
- Days until
- 21
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When is the next full moon?
A full moon occurs when the sun, Earth, and moon align so the near side is fully sunlit. Full moons repeat about every 29.5 days, but calendar dates drift because a synodic month is not an even number of days.
This calculator walks forward from your start date and reports the next date labeled full moon in our phase model, plus how many days you wait. If you start on a full moon, it finds the following one — not the same day.
Example: starting August 7, 2026, the next full moon falls within the next two to four weeks depending on where the current cycle sits. Use the result for planning; verify exact rise times locally for photography or events.
Official sources
Rates and formulas in this calculator reference the documentation below. Confirm current numbers on the source site before relying on them. Links do not imply endorsement by those organizations of Calcometry or this tool.
Common questions
Does the start date count as day zero?
Days until counts calendar days after your start date until the next full moon date. Starting the day before full moon typically shows 1 day until.
Why might this differ from a moon calendar app?
Apps may use precise ephemeris data and UTC phase instants. This page uses a simplified synodic-month walk — usually within a day of almanac dates.