Free tool
Feng Shui Ruler Calculator
Hong Kong contractors still size doors, desks, altars, and beds with the Luban ruler (魯班尺) — a measure that divides every 42.9 cm into eight named segments, four favorable and four not. Enter any dimension in inches or centimeters; we'll tell you where it lands and the nearest favorable range, useful when you're ordering joinery or furniture anyway.
Your result
Nearest favorable ranges
Renovating this year?
Dimensions are the easy part — where and when you cut, drill, and build matters more. This year's afflicted sectors make some walls better left alone until next Li Chun. A short conversation before the contractor starts can save an expensive redo.
Ask before the work startsPersonal reply within 12 hours, Mon–Sat (HKT).
How the ruler works
The Yang ruler (for homes of the living) repeats a cycle of eight segments: 財 Cai (wealth), 病 Bing (illness), 離 Li (separation), 義 Yi (righteousness), 官 Guan (authority), 劫 Jie (robbery), 害 Hai (harm), 本 Ben (origin) — favorable, unfavorable, alternating in the classical order. Each segment spans about 5.36 cm (2⅛ in). Carpenters traditionally aim doors and significant furniture at 財, 義, 官, or 本 — matching the segment's meaning to the object's purpose where possible: 財 for the safe and the shopfront door, 官 for the desk.
Treat it as tradition, not physics: a well-proportioned room with an "unfavorable" coffee table is a well-proportioned room. But when you are specifying a custom door or built-in anyway, choosing a favorable number costs nothing — which is exactly why Hong Kong joiners still carry the tape.
Related: where not to renovate this year · your home's facing mountain · glossary.