Lỗ Ban feng shui ruler
Vietnamese carpenters and builders still check sizes against the thước Lỗ Ban, a tape measure printed with a repeating band of red (lucky) and black (unlucky) segments. It is named after Lu Ban, the legendary master carpenter, and it is used when making a front door, an ancestor altar or a desk. Enter a size below to see which segment it falls on and, if it is an unlucky one, the nearest lucky size.
How to read the ruler
A Lỗ Ban tape repeats the same band over and over. Each band is split into large segments, each one lucky or unlucky, and each segment is split again into small sub-segments with their own names. What counts is the segment the final size lands on. Vietnamese craftsmen use three different bands, depending on what is being built:
52 cm ruler — openings (thông thủy)
Measures the clear opening (thông thủy) — the empty space you can pass through or see through, inside the frame. Used for main doors, gates, windows and stairwell openings. Tape measures in Vietnam often print this scale as “52.2 cm”; this tool uses the 52 cm cycle of the traditional table it is built on.
- Quý nhân Noble Helper lucky
- Hiểm hoạ Danger unlucky
- Thiên tai Disaster unlucky
- Thiên tài Heaven's Wealth lucky
- Nhân lộc Human Prosperity lucky
- Cô độc Solitude unlucky
- Thiên tặc Heaven's Thief unlucky
- Tể tướng Prime Minister lucky
42.9 cm ruler — solid pieces (dương trạch)
Measures solid objects for the living (dương trạch): desks, beds, wardrobes, kitchen counters, and the outer size of an altar table or cabinet.
- Tài Wealth lucky
- Bệnh Illness unlucky
- Ly Separation unlucky
- Nghĩa Righteousness lucky
- Quan Office & Rank lucky
- Kiếp Robbery unlucky
- Hại Harm unlucky
- Bản Foundation lucky
38.8 cm ruler — ancestral & yin (âm phần)
Measures things belonging to the dead and the ancestors (âm phần): graves and tombs, small shrines and the ancestor altar itself in many families.
- Đinh Descendants lucky
- Hại Harm unlucky
- Vượng Flourishing lucky
- Khổ Hardship unlucky
- Nghĩa Righteousness lucky
- Quan Office & Rank lucky
- Tử Death unlucky
- Hưng Rising Fortune lucky
- Thất Loss unlucky
- Tài Wealth lucky
Two practical tips: measure the exact dimension the ruler is meant for (the clear opening of a door, not the outside of its frame), and check width, height and depth separately — each one is read on its own.
A cultural reference, not a building rule
The Lỗ Ban ruler is a folk tradition. Many Vietnamese families care about it, and a carpenter will usually adjust a size by a centimetre or two to land on a lucky segment. It says nothing about strength, safety or accessibility. Real dimensions must follow building codes, fire-escape and accessibility rules, and the advice of your architect or engineer. Several versions of the ruler exist; if your craftsman uses a different one, follow his.
Lỗ Ban tapes are sold at VatPhamPhongThuy.com (Vietnamese store, ships within Vietnam).
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