About CycleCalcs
CycleCalcs computes the Moon, the planets and eclipses for the coordinates you give it, explains the cycles behind them, and names the conventions its numbers follow so you can check them. Every page and calculator is free, and the API has a free keyless tier. CycleCalcs began as a few fast calculators and grew into a full observatory bench: a live planetarium Sky Map, a Today in the Sky dashboard, an Eclipse Explorer, a Planet Parade Tracker, a pilotable flythrough of the solar system, a sorted reference of every major astronomical cycle, and a growing library of interactive lessons.
How the site works
Every position, phase, eclipse and rise time on CycleCalcs is computed live in your own browser from the same class of model that serious sky software uses. Nothing is looked up from a fixed table, there are no accounts, and the pages work the same for everyone. (The developer API, the calendar feeds, and the products you order or preview are computed on our servers, by design.) Positions are accurate to well under a degree, and the planetary models are reliable for roughly the years 1700 to 2200. The methodology page documents the models, sources and accuracy limits behind every tool.
What we care about
Real astronomy, plainly explained. The site covers what the sky actually does: why the Moon waxes and wanes, why eclipses come in seasons, why planets gather in parades, how the equinoxes drift around the sky in about 25,800 years. Where a topic has folklore attached, the pages say clearly what is established science, what is history, and what is neither.
No astrology, no forecasts. CycleCalcs computes where things are and says nothing about what they mean for your life, because planetary line-ups do not affect events on Earth. The one numerology calculator is presented as a classical interpretive tradition with a long history, and it is not science.
Honesty about limits. When a view is illustrative rather than measured (an enlarged planet, an artistic asteroid belt), the page says so. When a value is a long-term average or a contested estimate, the page says that too. Corrections are welcome and acted on.
What is free, and what is sold
CycleCalcs sells a few small printable products and paid API tiers, shows ads served by Mediavine, and its gear links are disclosed affiliate links. The gear links live on the gear and gifts page and in a small gear card on pages where gear helps the night, like ISO 12312-2 eclipse viewers on an eclipse page, and every card carries its own disclosure. You can also put the sky on your own site with the six free embeddable widgets: moon phase, sunrise and sunset, the next eclipse, a planet parade, what is up tonight, and a cosmic clock. The three products are the Moon Calendar 2027, Your Eclipse Day and The Moon That Night, each computed for a place you choose, and each one can be previewed before you buy. Nothing on the site asks you to sign in.
Privacy in one paragraph
Most of the astronomy on these pages runs on your device. The exceptions are the product previews, the API page and the widgets that get their figures from our servers, which send the place you choose to our servers to compute their answer. Choosing "use my location" or typing a place name is resolved against a place index served with this page. Preferences like your theme or saved location are remembered in your browser for your next visit. Pages that carry ads also load Mediavine's advertising script, which uses cookies to choose the ads. How the site handles data is set out in the Privacy Policy.
A note on accuracy
The tools aim to be correct and transparent, but they are provided for general educational and research use. They are not professional financial, investment, legal, or astrological advice. Orbital periods use standard mean values unless a page states otherwise.
Who runs CycleCalcs
CycleCalcs is published by CycleCalcs LLC, a limited liability company formed in the Commonwealth of Virginia, United States of America. The API terms of use and the privacy policy are the binding documents.
Questions, corrections or ideas? Email info@cyclecalcs.com. If you spot a number that looks wrong, please say which page and what you expected; those are the best emails we get.