The 24 Mountains and How to Read a Luopan
The compass in classical feng shui does not work in eight directions. It works in twenty-four, and the difference is not decoration. Two homes that both describe themselves as facing south can be up to 45 degrees apart, and several systems read those two homes differently — which is why the tradition records a facing direction to the nearest fifteen degrees rather than to the nearest of the eight points.
That ring of twenty-four divisions is called the 24 Mountains (二十四山). It is the working ring of the luopan (羅盤), the geomantic compass — the ring a facing reading is taken onto — and it is the resolution at which a facing direction is written down and a chart is built. This article explains what the ring is made of and how to take a reading onto it; the full list of the mountains with their degree ranges lives in the reference tables and is not repeated here.
1. What the ring is
Each of the eight directions — North, North-East, East, South-East, South, South-West, West, North-West — is a 45-degree span of the compass. The 24 Mountains divide each of those spans into three equal sectors of 15 degrees. Eight directions, three mountains each, twenty-four names.
A mountain is therefore not a thin line but a band. Saying that a building faces Zi (子) says that its facing falls somewhere inside a 15-degree sector centred on true north, and every calculation downstream takes that band as its input. The practical consequence is worth stating plainly: the ring asks for the sector, and reporting a raw degree further than the sector is a precision the chart does not use.
The 24 Mountains are a measuring instrument, not a system of interpretation. They carry no fortunes of their own. What they do is translate physically observed direction into the names that the Flying Stars, Ba Zhai and the home's own natal chart require.
2. Why 15 degrees rather than 45
The eight directions come from the eight trigrams, and a trigram is a coarse instrument: it tells you which side of the building has the most Yang, and nothing finer. The 24 Mountains exist because several classical systems need to distinguish between two facings inside the same trigram.
Two homes on the same street can both face "south" and be one and a half sectors apart. In the Flying Stars method the facing sector determines how the chart is built and which stars land in which palace, so the three southern mountains — Bing (丙), Wu (午) and Ding (丁) — behave differently even though all three are southern. Ba Zhai has the same requirement, since the personal directions are fixed points rather than wide spans, and a facing measured to 45 degrees could sit anywhere inside its group.
The finer division also raises the cost of a careless measurement. A 45-degree sector forgives a sloppy bearing; a 15-degree band does not. A reading that is wrong by half a sector produces a chart built on the neighbouring mountain, which is internally consistent and answers a different question from the one that was asked.
The rule of thumb: measure to the degree for the record, then name the mountain. If the two disagree about which side of a line the reading sits on, that is the boundary case described in section 5, and it needs a second measurement rather than a decision.
3. How the names are built
The twenty-four names are assembled from three elements of the classical system: the twelve Earthly Branches, eight of the ten Heavenly Stems, and four of the eight trigrams. Twelve plus eight plus four gives twenty-four, and the arrangement of the three kinds around the ring is not arbitrary.
3.1 The twelve branches
The twelve Earthly Branches stand at the twelve positions of the double-hour and month ring, and on the compass they keep the same order. The four cardinal branches — Zi (子) for north, Mao (卯) for east, Wu (午) for south and You (酉) for west — sit at the centre of the four cardinal directions. The other eight branches sit beside the corners.
3.2 The eight stems
The ten Heavenly Stems supply eight names. Wu (戊) and Ji (己) are the two Earth stems, and they belong to the centre of the grid rather than to a direction, so they do not appear on the ring at all. The eight that do appear are placed in pairs flanking the four cardinal branches: Ren (壬) and Gui (癸) either side of Zi, Jia (甲) and Yi (乙) either side of Mao, Bing (丙) and Ding (丁) either side of Wu, and Geng (庚) and Xin (辛) either side of You.
3.3 The four corner trigrams
The four corner directions take a trigram in the middle, flanked by two branches. These are the four diagonal trigrams of the Later Heaven arrangement: Gen (艮) for North-East, Xun (巽) for South-East, Kun (坤) for South-West and Qian (乾) for North-West. They are not one kind: Gen and Kun are the two Earth trigrams of the corners, while Xun is Wood and Qian is Metal — which is why the ring carries Earth at the diagonals without needing the two Earth stems that stay in the centre.
The result around the whole ring, reading north to north, runs Ren, Zi, Gui, Chou, Gen, Yin, Jia, Mao, Yi, Chen, Xun, Si, Bing, Wu, Ding, Wei, Kun, Shen, Geng, You, Xin, Xu, Qian, Hai. The names are also collected, with their characters, in the glossary. Four rows of the degree table, taken from the reference tables, look like this:
| Mountain | Character | Direction group | Degrees |
|---|---|---|---|
| Ren | 壬 | North | 337.5° – 352.5° |
| Zi | 子 | North | 352.5° – 7.5° |
| Gui | 癸 | North | 7.5° – 22.5° |
| Chou | 丑 | North-East | 22.5° – 37.5° |
4. How a facing direction is taken
4.1 Facing and sitting
Every building has two directions in a reading, and they are opposites. The facing direction is the most Yang side: the side with the main entrance, the most windows, the most activity, the open space that lets Qi gather. The sitting direction is the opposite, quieter, more solid side — the back of the building, so to speak. A building that faces south sits north, and the two are read as a pair.
This matters because the facing is what the 24 Mountains are recorded against, while the sitting direction carries its own meaning in several systems. Confusing the two is a common source of a wrong chart, and it is the reason the measurement is always taken by standing outside and facing away from the building, not by pointing a phone at the front door from the hallway.
4.2 Taking the reading
The measurement is straightforward but has to be done in the right place and clear of interference. The method is set out in full in how to determine your home's natal chart parameters; in outline, stand outside a few steps clear of the main entrance, turn your back to the building so that you look in the direction the building faces, hold the compass level and away from metal, and read the bearing.
Phones are the standard instrument now, and they are the standard problem. A magnetic compass responds to steel, and a modern building is full of it: reinforced concrete floors and columns, lift shafts, steel door frames, radiators, appliances, the car parked at the kerb, and the magnet in a phone case or a magnetic mount. Indoors, the reading can be deflected by tens of degrees without any warning. Two dedicated articles cover the fix — improving compass accuracy on Android devices and on iOS devices — and the short version is to take several readings in different places outdoors and compare them before trusting any of them.
What the measurement produces is one of the twenty-four names, plus the raw degree kept for the record. The name is what the systems consume; the degree is documentation, useful later if a reading looks wrong and the original measurement needs to be checked.
5. When the facing falls between two mountains
Fifteen degrees is a wide band, but a compass can still land on the line that separates two of them. That is the ambiguous case, and classical practice does not resolve it by choosing the nearer of the two.
The first response is to re-measure. A reading that sits exactly on a line is usually an artefact — a deflected needle, a phone held at an angle, a measurement taken too close to a steel frame — so the practitioner goes back outside, takes the bearing again from several positions, and checks whether the line result survives. If it does, the building is treated as a boundary type: a property whose facing sits on the division, traditionally handled as its own case rather than forced into one of the two neighbouring mountains. Some schools assign such properties their own chart convention; others advise reading both neighbours and treating the reading as qualified.
What not to do is invent a tolerance. There is no classical allowance that says a reading is "close enough" to a mountain to be rounded into it. Either the reading falls inside the sector or it falls on the line, and the answer to a line reading is a second measurement, not a rounding.
6. What the reading is used for
The mountain is the input, not the answer. Three things are built directly on it.
- The home's natal chart parameters. The facing direction and the period of construction are the two inputs of a Flying Stars natal chart, and the facing is recorded as a mountain.
- The Ba Zhai reading. The Eight Mansions system needs the building's facing to place its eight sectors, and it compares that grid with the personal directions of the Kua number.
- The Bagua overlay. Placing the nine sectors onto a floor plan is done from the same north, which is why the Bagua map and the compass reading have to agree before either is useful.
Where the charts disagree with each other, the disagreement is nearly always a measurement problem rather than a doctrinal one: two different norths were used for the same building.
7. Common mistakes
- Measuring the wrong side. The instrument is pointed at the door, but the building's Yang side is somewhere else, or the side with the main door is a service entrance. Fix the side first, then measure it.
- Measuring indoors. A reading taken in a hallway or beside a lift is a reading of the building's steel, not of its direction. This is the single most common cause of a chart that never quite fits the house.
- Using the flat when the block is meant. In a multi-storey building the classical default is the facing of the whole structure, taken at the main building entrance, not the facing of one unit's balcony or front door.
- Reporting degrees and stopping there. A bearing is an intermediate number. It becomes useful when it is named as one of the 24 Mountains, because that name is what the charts consume.
- Treating the sitting direction as a second facing. The sitting side is the opposite end of the same axis. Reading a chart as if the back of the house were its front produces results that look plausible and are wrong.
8. Frequently Asked Questions
Do I need a traditional luopan to read the 24 Mountains?
No. A luopan is a beautifully made instrument, but the work it does here is a single bearing, and a calibrated phone compass can supply that if it is used outdoors and away from steel. What a luopan adds is a physical ring you can align with the building; it does not change the result. The full degree table is in the reference tables, the 24 Mountains calculator converts a bearing into a mountain, and the Feng Shui tools collect the companion calculators.
What if my reading falls exactly between two mountains?
Re-measure before you decide anything. A line reading is usually caused by a deflected needle, a phone held out of level, or steel nearby, and a second set of readings taken outdoors normally resolves it. If the reading still lands on the line, the property is treated as a boundary case rather than rounded into one of the two neighbours.
Why does my phone compass give a different direction every time?
Because a phone compass is magnetic, and buildings are full of steel. Reinforced concrete, lift shafts, steel doors, radiators, appliances and cars all deflect it, and the effect is strongest indoors. Take several readings outdoors, a few steps clear of the building, and compare them; the Android and iOS guides cover the practical steps.
Which facing do I use for an apartment?
The classical default is the facing of the whole building, taken at the main entrance used by all residents, because that is where the structure collects Qi as a single object. The unit's own balcony or largest window is used by some practitioners as a secondary influence, but the building-facing method is the standard input for a natal chart. The alternatives are compared in how to determine your home's natal chart parameters.
Is the sitting direction as important as the facing?
It is the other half of the same axis, and different systems use it differently: some read the sitting side for support and stability, others mainly care that it is not confused with the facing. What matters universally is that the two are not mixed up, since a chart built on the sitting direction instead of the facing will be internally consistent and completely wrong.
