What goes in
The calculator needs a date, a local time and a place of birth. The place is used for one purpose: to find the time zone, including any daylight saving shift, that applied there on that date. The local time is then converted to a single universal time.
The same anywhereA Human Design chart has no houses, no rising sign and no dependence on latitude. Two people born at the same moment in different cities get the same chart.
Two moments, not one
Birth, in black. Where the Sun stands the moment you are born. The system calls this Personality.
Design, in red. The moment the Sun stood exactly 88 degrees of zodiac longitude behind that point, about three months earlier. The system calls this Design.
A sketch: your birth Sun can stand anywhere on the circle, and the red mark moves with it.
This is degrees, not days. Because the Sun moves a little faster in northern winter and a little slower in northern summer, 88 degrees corresponds to between roughly 86 and 92 days before birth, which is why people say "about three months".
Thirteen bodies at each moment
At each moment the calculator finds the zodiac longitude of 13 bodies. Longitudes are tropical, measured from the March equinox point.
| Body | Where it comes from |
|---|---|
| Sun, Moon | Their own positions |
| Earth | Opposite the Sun |
| North Node | The Moon's orbit |
| South Node | Opposite the North Node |
| Mercury, Venus, Mars, Jupiter | Their own positions |
| Saturn, Uranus, Neptune, Pluto | Their own positions |
In shortThat gives 26 positions in all, 13 from Personality and 13 from Design.
Sixty-four gates, six lines
The zodiac circle is cut into equal pieces:
| Piece | How many | How wide |
|---|---|---|
| Gate | 64 around the circle | 5.625 degrees |
| Line | 6 in each gate | 0.9375 degrees |
The order of the gates around the circle is fixed and does not follow their numbers. Gate 41 starts at 2 degrees of Aquarius, and the rest follow.
For each of the 26 positions, the calculator finds the gate and the line. The result is a list of activations, each written as gate.line, such as 34.2. The calculator stops at lines. The system divides further, into colors, tones and bases, and we do not use those.
Gates become channels and centers
The 64 gates are spread across nine centers, and certain pairs of gates form 36 channels.
- A complete channel. Both of its gates are active, from either moment or one from each. It defines the two centers it joins.
- An open center. A center without a complete channel.
Type, authority and definition then come from rules applied to the defined centers. Which motor is joined to the throat, and which center ranks highest, are mechanical checks. The guide to reading your chart lists them in order.
Why only twelve profiles exist
The profile uses the line numbers of the Sun at both moments. The 88-degree gap fixes how they relate. It equals 93.87 lines, and since line numbers repeat every six lines, the design line sits either two or three steps after the birth line, wrapping from 6 back to 1.
| The step | How often | Profiles it gives | Each covers |
|---|---|---|---|
| Two lines | 13 out of 15 | 1/3, 2/4, 3/5, 4/6, 5/1, 6/2 | About 14 percent |
| Three lines | 2 out of 15 | 1/4, 2/5, 3/6, 4/1, 5/2, 6/3 | About 2 percent |
The last column assumes births are spread evenly across the year. These are rough figures: rounded like this they add up to 96 percent, not 100. This is our own arithmetic from the definition and not a survey.
What affects accuracy
The calculation is the part we can test. Your birth time is the part we cannot.
| What could be off | How much | What it can change |
|---|---|---|
| The astronomy | Within 0.5 arcseconds of NASA JPL Horizons, 1 arcsecond for the lunar node, at 80 test moments from 1900 to 2030 | Only a body lying on the very edge of a line |
| The chart rules | 236 published charts reproduced, from three other calculators. Four differ on one item each, and JPL or the other calculators back our value | Rare: a body very near a gate boundary, or a convention such as the type of lunar node |
| Birth time, the Moon | The Moon crosses a line about every 1.7 hours and a gate about every 10 hours | Near a gate edge, a few minutes can change the gate. That may complete or break a channel and shift a center, an authority or even the type, most visibly for Reflectors |
| Birth time, the Sun | The Sun's line changes roughly once a day | The profile, and only rarely |
| The time zone | Rules before about 1970 are patchy in some regions: a shift of an hour is possible even when the clock time is right | The same as a wrong birth time |
Try thisIf you are unsure of the time, try a few values across the range you think is possible and watch which parts of the chart move.
What this site does not do
TwoInks does not give personal readings or predictions, and the pages describe the system in general. Nothing here is health, medical, legal or financial advice, and a chart should not be used to make decisions about those, or about other people, such as hiring.
An honest note on Human Design
- Where it came from. The system was introduced in 1987 by a man who later took the name Ra Uru Hu, after what he described as a mystical experience. It combines ideas from astrology, the I Ching, the chakra system and Kabbalah with references to modern physics, including claims about neutrinos.
- What the evidence says. There is no scientific evidence that the type, authority or profile calculated from a birth chart predicts behavior, health or how well someone's decisions turn out.
- What the physics says. The physical explanations offered for it, such as neutrinos carrying a person's design, are not supported by physics.
- Why it can feel right. Descriptions of the types are written in terms broad enough that many people recognize themselves, which is a well-known effect in personality readings of all kinds.
None of that stops people from finding the vocabulary useful. Many use it as a structured prompt to ask what they notice in their own lives, and a prompt can be useful whether or not the system behind it is true. We write the pages in that spirit: "according to Human Design" is meant literally.
RememberTest any idea against your own experience, and do not give the system authority it has not earned.
To read your own chart, start with the TwoInks calculator. To understand the output, see the guide, and for what this site is and is not, the about page.
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