Moon Age Calculator

Calculate the moon's age in days since the last new moon for any date.

Select Date

How It Works

Enter a date. The calculator determines how many days have passed since the last new moon — this is the "moon age." A value near 0 means new moon; near 14.77 means full moon; near 29.53 means back to new moon.

Formula

Moon Age = phase fraction × 29.53059 days

Frequently Asked Questions

What is moon age?

Moon age is the number of days since the last new moon. It ranges from 0 (new moon) to about 29.53 days (next new moon).

What moon age corresponds to a full moon?

A full moon occurs around moon age 14.77 days (halfway through the 29.53-day cycle).