How to take a compass bearing indoors
Published 2026-08-20
Stand in the main doorway looking out, hold the phone level and square to the door frame, and write the number down. Then do it twice more, from a step or two away. If the three readings agree within a degree or two, that is your facing bearing. If they do not, you do not have one yet.
Everything Eight Mansions (八宅, Ba Zhai) says about your home is built on that single number, so it is worth ten minutes rather than ten seconds.
What “facing” means before you measure anything
The facing direction belongs to the building, not to the room you are standing in. It is the side the front of the building looks out on — usually the side with the main entrance, or the side with the main view if those differ. Sitting is the opposite 180°, and the house is named after its sitting side, so a house facing south sits north.
Two consequences. A bearing taken along the wall of a back bedroom is not the house bearing. And if you genuinely cannot tell which side is the front — a corner unit with two equal entrances, a building whose main view faces away from its door — that ambiguity is a bigger problem than measurement error, because the two candidates are usually 90° apart.
Why the middle of the room is the worst place to stand
A phone compass reads the magnetic field where the phone is, and indoors that field is not just the earth’s. Steel in the structure, wiring in the walls, and the magnets in speakers and laptops all pull the reading. A refrigerator or a steel door frame can pull it hard.
That gives a short list of things to do:
- Take the reading outdoors in front of the building if you can, standing back from the facade.
- If you cannot, use a doorway or an open window rather than the center of the room.
- Put down the keys, step away from the laptop, and take the phone out of any case with a magnetic closure.
- Hold the phone flat and level, with its long edge parallel to the door frame or the wall you are measuring. You are measuring which way the wall looks, not which way you happen to be standing.
- Take three readings from slightly different spots. One reading tells you nothing about its own reliability.
What counts as good enough
Eight Mansions palaces are 45° wide, so their edges fall at 22.5°, 67.5°, 112.5° and so on. What matters is not how tight your three readings are in the abstract, but whether they sit on the same side of the nearest edge.
Two examples of three readings each, run through the site’s own house calculation:
| Readings | Houses they produce | Verdict |
|---|---|---|
| 178°, 180°, 182° | Kan house, Kan house, Kan house | one answer, all three over 20° clear of an edge |
| 198°, 201°, 205° | Kan house, Kan house, Gen house | two answers, in opposite groups |
The first spread is four degrees wide and completely harmless. The second is seven degrees wide and straddles the edge at 202.5°, which means you are holding two candidate charts — one East group, one West group — with nothing in Eight Mansions to choose between them. Averaging to 201.3° would produce a Kan house, and it would be a Kan house held together by rounding.
When that happens, go back outside and measure again rather than picking. The compass bagua map reports how far your bearing is from the nearest edge and warns you when it is within three degrees, which is the check you want before you read anything else on the page.
Magnetic north or true north
The two norths differ by an amount that depends on where you are standing, and a phone compass may be reporting either one — some apps let you switch, and they do not all default to the same convention.
This site does nothing about it. There is no declination correction anywhere in the code. The tool takes the number of degrees you type, works out which 45° palace it falls in, and builds the chart from that. So your result is in whichever convention your compass was set to when you read it, and method and assumptions does not claim otherwise.
The traditional instrument, the luopan, is a magnetized needle, so the readings the compass tradition was built on were magnetic ones. And whichever convention you use, use the same one for every reading — the difference between the two matters only when it is larger than your distance to the nearest palace edge, and the tool tells you what that distance is.
If you cannot get a bearing at all
Some homes do not give you one. A windowless interior unit, a strong local magnetic disturbance, a building whose front is genuinely ambiguous — in those cases the compass method has nothing to work with, and guessing the bearing to keep the tool happy produces a chart that looks identical to a real one.
The three-door bagua taught in the West as BTB or Black Sect needs no compass at all: it lines its nine squares up with the front door instead. That is a different school reaching different conclusions about the same home, not a fallback version of this one, and the two should not be mixed in a single plan. Which of them to follow is your call, and the two things called a bagua map lays out what each can answer.
What a good bearing does not buy you
A stable bearing means the chart you get is the chart your building actually has. It does not mean the chart predicts anything. Eight Mansions labels sectors and directions, this site reports those labels, and neither of us claims that a favored sector changes an outcome you could measure.