How MirrorChart calculates your Human Design chart

MirrorChart works out where the Sun, Moon and planets were at the moment of your birth, and again at the moment the Sun was exactly 88 degrees of its orbit earlier. It then converts each position into a gate and line on the Human Design wheel and applies the system’s standard rules to get your Type, Authority, Profile and Definition.

What you enter, and why each part matters

A chart needs a birth date, a birth time and a birth place. The place is used only to find the right time zone, because a clock time is meaningless until it is converted to a universal moment. The time matters most: the Moon moves about half a degree per hour, which is enough to change a line, and sometimes a whole gate, within a few hours.

Step 1: Time zones, including daylight saving as it was

We convert your local birth time to UTC using the historical time zone rules for your birth place, not today’s rules. A birth in London in April 1976, for example, happened during British Summer Time, so 22:30 local time is 21:30 UTC. If your local time did not exist (clocks jumped forward) or happened twice (clocks went back), we say so on your chart instead of silently guessing.

Step 2: Planet positions

We calculate the ecliptic longitude of the Sun, Earth, Moon, the lunar nodes and the planets from Mercury to Pluto. The positions come from an open-source astronomy library that runs in your browser, so your birth details are not sent to a server for this step.

The Earth is placed exactly opposite the Sun, and the South Node exactly opposite the North Node. By default we use the true (osculating) lunar node, which follows the Moon’s actual orbit, rather than the smoother mean node. The two can differ by a fraction of a degree and occasionally land on different lines.

Step 3: The Design date

Your Design side is calculated for the moment the Sun was 88 degrees earlier on the ecliptic than at your birth. This is 88 degrees of solar arc, not 88 days. Because the Earth’s speed changes through the year, the gap is usually between about 85 and 93 days. We solve for the exact moment numerically instead of subtracting a fixed number of days.

Step 4: From a position to a gate and line

The Human Design wheel divides the zodiac into 64 gates of 5.625 degrees each, and each gate into 6 lines of 0.9375 degrees. Gate 25 begins at 28°15′ Pisces and the gates then follow a fixed order around the wheel. A planet’s longitude therefore lands on exactly one gate and one line. Each chart has 13 activations on the Personality (birth) side and 13 on the Design side.

Step 5: Channels, centers and the headline results

• Channels. A channel is defined when both of its gates are activated. There are 36 channels.
• Centers. A center is defined when at least one complete channel touches it. Otherwise it is open.
• Type. Reflector if no center is defined. Otherwise Generator or Manifesting Generator if the Sacral is defined (Manifesting Generator when the Throat connects to a motor center), and Manifestor or Projector if it is not.
• Authority. The first defined center in the order Solar Plexus, Sacral, Spleen, Heart, then G connected to the Throat. A Reflector has Lunar authority, and a chart with none of those has Mental (sometimes called no inner authority).
• Profile. The line of your Personality Sun over the line of your Design Sun, for example 2/4.
• Definition. How many separate groups your defined centers form: Single, Split, Triple Split or Quadruple Split.

How we checked it

We tested the astronomy against an independent, professional-grade ephemeris on 300 random dates between 1920 and 2040. Planet, Moon and mean-node positions agreed to within 0.01 degrees, and the true node to within 0.02 degrees. That is far finer than a single line.

We also compared complete charts with the free calculator of the organisation behind the original Human Design software, across four different birth dates and places, covering a Projector, a Generator, a Manifestor and a Reflector, one of them born during daylight saving. Type, Authority, Definition, Profile and the four Incarnation Cross gates matched in every case. On one chart we also compared all 26 gate and line activations with two calculators, and they matched. Four charts is a good sign, not a guarantee, so if you ever find a mismatch we want to hear about it.

Where a chart can still be wrong

• The birth time. A time that is a few minutes off can change your Profile or a gate. When that could affect your result, MirrorChart tells you which parts might change.
• The birth place. We use the place you pick to determine the time zone. Check it if you were born near a border or in a region with unusual historical time rules.
• Different calculators. Sites can differ on the node (true versus mean) or on rounding at gate boundaries. If a planet sits right on a boundary, two honest calculators can disagree.

What the chart can and cannot tell you

The astronomy is measurable. The interpretation is not: Human Design is a framework people use to reflect on how they decide and relate to others, and there is no scientific evidence that it predicts behaviour or outcomes. Treat your chart as a prompt for self-reflection, try what resonates, and leave what does not.