Private astrology calculator

Find your Sun, Moon and rising signs

Your Big Three are your Sun, Moon and rising signs — the placements from your birth city and time that shape a chart's tone the most; enter them here and all three are calculated in your browser.

Your birth details

Enter the astronomical moment

Pick the birthplace — the zone follows.

Birth place

An offline city list. Nothing goes online.

Set the place manually

Coordinates are optional here. A recognized IANA time zone (for example Europe/Warsaw) is enough to apply the correct historical offset, but the rising sign and houses need latitude and longitude too.

Birth date
Birth time

Pick a city to apply its time zone

The birth moment and coordinates stay in this tab.

Ready when you are.

Two Skies in ConversationLay one chart over another — every contact, house and reading between you.Compare two skies →carries your moment as Person AThe Chart Between YouOne chart for a pairing — the midpoint, or a real Davison sky.Cast the chart →carries your moment as Person AThe Sky Over Yours, TodayWhich planets are touching your chart now — and when each contact is exact.See today's sky →carries date · time · city

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Direct answer

What you need

Nothing is uploaded or placed in the URL. A cast is kept only in this tab's own memory — long enough for "Read next" — until you close the tab.

Method & limits

Astronomy first, symbolism second.

Calculations use the tropical zodiac and geocentric apparent ecliptic positions. A rising sign cannot be calculated responsibly without an exact time and place; near a sign boundary, a small input error can change the result.

Frequently asked questions

How accurate is this Big Three calculator?

The Sun and Moon signs come from Astronomy Engine to within about one arcminute of precision for the date and time you enter, and the same is true of the rising sign once a birth time and place are supplied. The rising sign is the most sensitive of the three to a small error in the recorded time.

What happens if I do not know my exact birth time?

The Sun sign is unaffected, since it is effectively fixed for the whole day. The Moon sign is computed from a neutral midday placeholder and can occasionally be off by one sign if the Moon changed sign that day, and the rising sign is left out unless you use the Estimate with sunrise option, since it needs a real clock time to calculate.

What is a cusp birthday, and which of my three signs does it affect?

A cusp birthday usually refers to the Sun, when your birth date falls close enough to a sign change that the exact hour and time zone decide it. The Moon changes sign roughly twelve times a month and the rising sign roughly every two hours, so both are far more likely to sit on a cusp than the Sun is.

Does this use the tropical or sidereal zodiac?

All three signs here use the tropical zodiac, the seasonal system where zero degrees Aries marks the spring equinox, rather than the sidereal zodiac, which is anchored to the visible constellations. Most Western astrology, including the Big Three idea, is built on the tropical convention.

Why do I need to enter a birthplace for my Big Three?

The birthplace sets the historical time zone that converts your entered local time into the correct astronomical instant, and it sets the horizon the rising sign is measured against. Without it, the Sun and Moon signs can still be calculated, but the rising sign cannot. For a birth before 1970 in a small set of zones — mostly the Low Countries, Scandinavia and the former Yugoslavia — the historical rules come from the tzdata backzone (release 2025c), compiled into the site.

Is my birth information sent anywhere?

No. The calculation runs entirely in your browser using a local astronomy library and an offline city list; nothing about your birth date, time or place is uploaded, stored on a server, or placed in the page URL.