How to Calculate Moon Phase
What is Moon Phase?
The moon phase on any date can be calculated using the synodic period (29.53 days) — the time for the Moon to return to the same phase. Starting from a known New Moon date, you calculate how many days have elapsed and where that falls in the lunar cycle.
Step-by-Step Guide
- 1Use a known New Moon as a reference (e.g., 6 January 2000)
- 2Calculate days elapsed from reference to target date
- 3Divide by synodic period (29.53058 days) and take the remainder
- 4The remainder tells you the phase: 0=New, 7.4=First Quarter, 14.8=Full, 22.1=Last Quarter
Worked Examples
Frequently Asked Questions
What is Moon Phase?
The moon phase on any date can be calculated using the synodic period (29. 53 days) — the time for the Moon to return to the same phase
How accurate is the Moon Phase calculator?
The calculator uses the standard published formula for moon phase. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.
What units does the Moon Phase calculator use?
This calculator works with inches. You can enter values in the units shown — the calculator handles all conversions internally.
What formula does the Moon Phase calculator use?
The calculator applies the standard formula for this type of calculation. See the 'How It Works' steps above for the detailed formula breakdown.
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