What do I need to calculate my natal chart?

You need your birth date, your exact birth time (hour and minute), and your birth city. If you don't know your birth time, you can still see your Sun and Moon signs, but your Rising sign requires accurate time.

Is my birth data uploaded to your server?

No. All calculations run entirely in your browser using local astronomical algorithms. Your birth date, time, and location are never sent to any server — not even ours. The free Natal Chart Calculator on fastool.io operates with zero data collection: your birth information stays on your device.

How accurate are the calculations?

Planetary positions use JPL DE ephemeris data with sub-arcminute accuracy, matching professional astrology software. Rising sign calculations depend on your birth time accuracy — even 1-2 minutes can matter.

Why is my Rising sign different on other websites?

Rising sign discrepancies usually come from two factors: slightly different birth coordinates (make sure your city is correct) or different house systems (we use Placidus by default, which is the most common).

Calculate Your Natal Chart — Free Birth Chart Calculator

Know Your Big Three — Sun, Moon, and Rising Sign

All calculations run locally. Your birth data never leaves your browser.

All natal chart calculations run locally in your browser. Your birth date, time, and location are never sent to any server. We use Sentry only for crash reporting — no personal data is collected.

About Natal Charts

What Is a Natal Chart?

A natal chart (or birth chart) is a map of where the planets were in the sky at the exact moment and location of your birth. It shows the Sun, Moon, and planets projected onto the zodiac wheel.

Wikipedia: Natal astrology

What Are the Big Three?

Your Sun sign represents your core identity, your Moon sign governs your emotional world, and your Rising sign (Ascendant) is the 'mask' you present to the world. Together, they form the foundation of your natal chart.

Learn more about the Big Three

How Is the Rising Sign Calculated?

The Rising sign is the zodiac sign that was on the eastern horizon at your birth. It depends on your exact birth time and location — even a few minutes difference can change it.

Wikipedia: Ascendant

Planetary Positions & Houses

Planets are placed in zodiac signs (showing their expression) and in houses (showing which life area they influence). House positions depend on the Placidus system by default.

Wikipedia: House (astrology)

Frequently Asked Questions

What do I need to calculate my natal chart?: You need your birth date, your exact birth time (hour and minute), and your birth city. If you don't know your birth time, you can still see your Sun and Moon signs, but your Rising sign requires accurate time.
Is my birth data uploaded to your server?: No. All calculations run entirely in your browser using local astronomical algorithms. Your birth date, time, and location are never sent to any server — not even ours. The free Natal Chart Calculator on fastool.io operates with zero data collection: your birth information stays on your device.
How accurate are the calculations?: Planetary positions use JPL DE ephemeris data with sub-arcminute accuracy, matching professional astrology software. Rising sign calculations depend on your birth time accuracy — even 1-2 minutes can matter.
Why is my Rising sign different on other websites?: Rising sign discrepancies usually come from two factors: slightly different birth coordinates (make sure your city is correct) or different house systems (we use Placidus by default, which is the most common).

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