Calculadora de Fases da Lua
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
fase = (dias mod 29,53) / 29,53
About this calculator
The Moon Phase Calculator determines the current lunar phase based on the synodic cycle of approximately 29.53 days. The calculation uses the number of days since a reference new moon and applies the formula: phase = (days mod 29.53) / 29.53. The result is a value between 0 and 1, corresponding to one of eight main phases: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent.
This tool is useful for amateur astronomers, photographers, farmers, or anyone interested in knowing the moon phase on a specific date. For example, when planning astronomical observations, a full moon can hinder star viewing, while a new moon is ideal. In agriculture, some farmers follow the lunar calendar for planting or harvesting.
Cautions: the calculator considers an average cycle and does not account for orbital variations or time zones. For absolute accuracy, consult an official lunar calendar. Additionally, the calculated phase is approximate, as the actual cycle may vary slightly. Remember that the new moon occurs when the phase value is near 0 or 1, and the full moon near 0.5.
Frequently asked questions
How does the calculator determine the moon phase?
It counts the days since a reference new moon, divides by the 29.53-day cycle, and uses the remainder to map the phases.
Does the calculator consider time zones?
No, it uses an average cycle and does not adjust for time zones. For local accuracy, consult a lunar calendar specific to your region.
What phase corresponds to the value 0.5?
The value 0.5 corresponds to the full moon. Values near 0 or 1 indicate a new moon.
Can I use this calculator for agriculture?
Yes, many farmers use lunar phases as a reference, but remember it is an approximation. Also consult a local agricultural calendar.
Does the calculator work for past or future dates?
Yes, you can enter any date. The calculation is based on the cycle, regardless of the date.