The Astrolium midpoint calculator returns the full natal midpoint grid — Sun/Moon, AC/MC, and every pair of bodies — with the 90-degree dial readout, in under 30 seconds. Math runs on the Swiss Ephemeris in your browser. No login, no email, no upload.
Midpoints read inside the natal chart feature and run against current transits in predictive timing. For the chart's hierarchy of weighted bodies, see the dominant planet calculator. For the ruler of the 1st in traditional readings, see the chart ruler calculator.
What you get
A midpoint is the point exactly halfway between two other points on the ecliptic. Every pair of bodies produces one midpoint. With 10 classical planets plus the 4 angles and the lunar nodes, the full grid has more than 100 midpoint positions. Most don't matter. The ones that matter are the ones where a third natal body or current transit sits within a degree.
Reinhold Ebertin's Combination of Stellar Influences and Alfred Witte's Uranian school built the technique. Cosmobiology — Ebertin's method — uses midpoints almost exclusively, reading them on the 90-degree dial where conjunctions, squares, and oppositions fold into a single contact. For the traditional approach to weighting bodies in the chart, see the hellenistic astrology guide.
What the midpoint means in astrology
A natal midpoint is dormant on its own. It activates when a third point — natal, transiting, or synastric — sits on it.
The Sun/Moon midpoint is the most-cited single midpoint in the Uranian tradition. Ebertin called it the relational core. A transit or progression to Sun/Moon often coincides with a defining partnership event. In synastry, a partner's Venus or Sun on your Sun/Moon midpoint within 1 degree is the strongest non-classical relational signal in the chart — pair this read with the synastry calculator to see the full inter-aspect grid alongside midpoint contacts.
The AC/MC midpoint names how the chart's outward identity and public role integrate. A natal Saturn on AC/MC reads as a chart that builds slowly in public.
The Mars/Saturn midpoint is the work-discipline point — pressure, capacity for sustained effort, sometimes the body's stress response. Ebertin paired it with health timing.
Twelve to fifteen central midpoints carry most of the reading. Astrolium surfaces them first and lists the rest below.
How Astrolium calculates midpoints
The math runs on the Swiss Ephemeris DE431. Each midpoint is computed as the shorter arc between two points — the direct midpoint at the halfway position, and the indirect midpoint 180 degrees opposite. Both register on the 90-degree dial. Absolute positions match Solar Fire, Janus, and Cosmobiology software to the arc-second.
Astrolium supports 4 house systems — Placidus, Whole Sign, Koch, Equal. House assignment changes per system; the midpoint position itself does not.
Use midpoints in your client work
Two practical contexts.
When the chart looks generic — major aspects loose, no obvious headline — midpoints often surface the real structure. A Sun/Moon midpoint conjunct natal Saturn within 30 minutes of arc names the chart's central relational tension more cleanly than any aspect would. Reading the central midpoints is what makes the difference between a textbook reading and one the client recognizes.
When timing the next 12 months, transits to natal midpoints are the second pass after transits to natal planets. A transit Jupiter on natal Sun/Moon midpoint reads as a relational opening event with a precise window. Pair the calculator with the predictive timing feature to see the schedule across the year.
After the calculator
Midpoints don't replace the rest of the chart. They sharpen it. The full reading is the standard wheel plus the midpoint grid plus the dial.
For the chart wheel with the midpoint layer enabled, see the natal chart feature. For the timing layer where midpoints get activated by transit, see predictive timing. For the chart's hierarchical structure, see the dominant planet calculator and the chart ruler calculator. For a related Uranian technique that converts aspects into conjunctions for pattern analysis, see the harmonic chart calculator.