What is the Lu Ban Ruler? How to Read Auspicious and Inauspicious Measurements in Feng Shui

Jul 31, 2026

Q: What is the Lu Ban Ruler? What is it used for?

A: The Lu Ban Ruler (鲁班尺, lǔ bān chǐ), also known as the "Ban Ruler," "Door Ruler," or "Carpenter's Square," is a traditional Chinese measuring tool used in architecture and woodworking. According to legend, it was invented by Lu Ban (鲁班) during the Spring and Autumn Period. The Lu Ban Ruler is more than just a measuring device — it is a powerful Feng Shui instrument used to determine lucky dimensions for buildings and furniture.

The Origins of the Lu Ban Ruler

Lu Ban (鲁班, approximately 507–444 BC) was the most celebrated master craftsman in ancient China, revered as the "Patron Saint of Carpenters." While the Lu Ban Ruler is traditionally attributed to him, the version used today was actually refined and developed over centuries by generations of Feng Shui masters.

Cultural Context: In traditional Chinese culture, dimensions are not merely practical — they carry energetic meaning. The Lu Ban Ruler bridges the practical and the metaphysical, suggesting that the size of a doorway or piece of furniture can influence the fortune of those who use it.

Uses of the Lu Ban Ruler

1. Determining Door Dimensions The primary use is measuring doors, including main entry doors, interior doors, and windows.

2. Determining Furniture Dimensions Bed, desk, chair, and cabinet sizes can also be determined using the Lu Ban Ruler.

3. Determining Building Dimensions House width, height, and depth can be referenced against the Lu Ban Ruler.

4. Feng Shui Layout In Feng Shui arrangements, the Lu Ban Ruler helps determine lucky distances and sizes for object placement.

Q: What is the structure of the Lu Ban Ruler? What do the characters on it mean?

A: The structure of the Lu Ban Ruler is complex, but easy to understand once you learn it.

Two Types of Lu Ban Ruler

1. Door Ruler (门公尺) — For Yang Dwellings

Used to measure doors in living spaces. It is divided into eight equal sections, each corresponding to a specific auspicious or inauspicious meaning.

2. Ding Lan Ruler (丁兰尺) — For Yin Dwellings

Used for measuring Yin Dwelling (阴宅, yīn zhái, i.e., graves) and ancestral spirit tablets. It also has eight sections, but the meanings differ from the Door Ruler.

Cultural Context: The distinction between the Door Ruler and Ding Lan Ruler reflects the broader Yin-Yang principle in Feng Shui — the Yang (living) world and Yin (ancestral/spiritual) world each have their own measurement standards.

The Eight Sections of the Lu Ban Ruler

The eight sections each correspond to a single character:

Wealth (财), Sickness (病), Separation (离), Righteousness (义), Official (官), Robbery (劫), Harm (害), Auspicious-Ben (吉本)

Among these:

Auspicious characters: Wealth (财), Righteousness (义), Official (官), Auspicious-Ben (吉本)
Inauspicious characters: Sickness (病), Separation (离), Robbery (劫), Harm (害)

Meaning of Each Character

1. Wealth (财) — Auspicious Represents fortune and prosperity. Ideal for main doors, living rooms, and entryways.

2. Sickness (病) — Inauspicious Represents illness and disaster. Should be avoided.

3. Separation (离) — Inauspicious Represents parting and estrangement. Should be avoided.

4. Righteousness (义) — Auspicious Represents loyalty and meaningful relationships. Ideal for studies and bedrooms.

5. Official (官) — Auspicious Represents career advancement and professional success. Ideal for offices and studies.

6. Robbery (劫) — Inauspicious Represents loss and financial disaster. Should be avoided.

7. Harm (害) — Inauspicious Represents injury and damage. Should be avoided.

8. Auspicious-Ben (吉本) — Auspicious Represents destiny and supreme good fortune. The most auspicious measurement of all.

Subdivisions of Each Character

Each character is further divided into four smaller sections, each with its own auspicious or inauspicious meaning. For example, under "Wealth (财)" you will find: Virtue of Wealth (财德), Treasury (宝库), Six Harmonies (六合), and Welcoming Fortune (迎福) — all auspicious meanings.

Q: How Do You Read Auspicious and Inauspicious Measurements? How Do You Measure?

A: Follow these steps to use the Lu Ban Ruler:

Step-by-Step Usage

Step 1: Identify the Object to Measure Decide what you are measuring — a door, bed, desk, or other item.

Step 2: Take the Measurement Use the Lu Ban Ruler to measure the actual dimensions. Note that one Lu Ban chi is approximately 42.9 centimeters in modern usage, though this may vary slightly by version.

Step 3: Read the Auspicious Meaning Look at which character your measurement falls on to determine fortune.

Choosing Auspicious Dimensions

1. Main Doors

The main door is the "Qi mouth (气口)" of a home — the primary entry point for energy. Auspicious dimensions should fall on Wealth (财), Righteousness (义), Official (官), or Auspicious-Ben (吉本).

Recommended dimensions:

Width: Land on "Wealth (财)" or "Auspicious-Ben (吉本)"
Height: Land on "Righteousness (义)" or "Official (官)"

2. Interior Doors Interior door sizes should also land on auspicious characters, especially Wealth (财) and Auspicious-Ben (吉本).

3. Windows Window dimensions follow similar principles as doors — favor Wealth (财) and Auspicious-Ben (吉本).

4. Beds Bed dimensions should land on Wealth (财), Righteousness (义), or Auspicious-Ben (吉本), and avoid Sickness (病) or Separation (离).

5. Desks Desk dimensions favor Righteousness (义), Official (官), or Auspicious-Ben (吉本) — especially helpful for students and professionals seeking career growth.

6. Spirit Tablets Spirit tablet and altar dimensions should use the Ding Lan Ruler, landing on auspicious characters.

How to Adjust Dimensions

If your measurement lands on an inauspicious character, try these remedies:

1. Add or Subtract a Few Centimeters Fine-tune the measurement to land on an auspicious character.

2. Change the Measurement Method In some cases, you can change what you measure — measuring the inner frame instead of the outer frame, for example.

3. Use Feng Shui Items to Dissolve Sha If adjustments are impossible, place Five Emperor Coins (五帝钱) or other protective items in the corresponding location to neutralize the harmful energy.

Remember: Feng Shui seeks to balance Yin and Yang energies — the dual forces that shape all existence.

How to Apply This at Home

Measure your main entry door first — this is your highest-priority Feng Shui adjustment
Check your bed dimensions — since you spend a third of your life sleeping, this measurement matters
Verify before ordering custom furniture — it's easier to choose lucky dimensions at the design stage than to fix them later
Document your measurements — keep a simple record of what lands where so you can plan future purchases

Quick Tips:

The "Qi mouth (气口)" refers to the energy gateway of your home — your main entrance. Prioritize this measurement above all others

Avoid building or installing new doors during inauspicious periods like Three Sha (三煞) positions if possible

Always cross-check with a standard tape measure alongside the Lu Ban Ruler to verify both physical and metaphysical dimensions

Balance the Five Elements: Incorporate Wood, Fire, Earth, Metal, and Water in your décor for harmonious energy

Q: Is the Lu Ban Ruler Still Useful in Modern Interior Design? How Do You Apply It?

A: The Lu Ban Ruler still has practical value in modern home decoration, but should be applied with flexibility:

Lu Ban Ruler Applications in Modern Design

1. Main Door Dimensions Main entry door sizes in modern homes are typically determined by developers and cannot be changed. However, during renovation you can measure and verify, and if the dimensions are inauspicious, apply these remedies:

Hang Five Emperor Coins (五帝钱) above the door
Place Five Emperor Coins under the doormat
Affix a "Fu (福)" character on the inside of the door

2. Interior Door Dimensions Interior doors (bedroom, bathroom, kitchen doors) can be custom-ordered to auspicious dimensions. If the existing size is inauspicious, you can adjust the door frame size.

3. Furniture Dimensions When commissioning custom furniture, choose auspicious dimensions according to the Lu Ban Ruler — especially for major pieces like beds, desks, and sofas.

4. Window Dimensions Window sizes can reference the Lu Ban Ruler, but in modern construction these are usually determined by architects with limited room for adjustment.

Modern Versions of the Lu Ban Ruler

Several versions are currently available:

1. Traditional Lu Ban Ruler 42.9 cm per chi — suitable for traditional architecture

2. Taiwan Lu Ban Ruler 43.2 cm per chi — used in Taiwan and southern Fujian regions

3. Metric Lu Ban Ruler A metric-converted version of the traditional Lu Ban Ruler — designed for modern use

Limitations of the Lu Ban Ruler

1. Dimensional Constraints Modern building and furniture sizes are constrained by many factors and cannot always conform to Lu Ban Ruler standards.

2. Version Variations Different versions of the Lu Ban Ruler have slight differences in length — choose the version that aligns with local custom.

3. Excessive Obsession Over-fixating on Lu Ban Ruler dimensions may result in impractical designs or wasted space.

Practical Recommendations

1. Prioritize Function First Meet functional needs first, then reference the Lu Ban Ruler for auspicious adjustments.

2. Focus on the Main Door The main door is the Qi mouth (气口) of the home, and its auspicious dimensions carry the greatest weight.

3. Stay Flexible If a dimension cannot be auspicious, use other remedies — don't become obsessed.

4. Consult a Professional For precise Lu Ban Ruler measurements, consult a professional Feng Shui master or experienced carpenter.

Summary: The Lu Ban Ruler is an important part of traditional Chinese architectural culture. It reflects ancient wisdom about the relationship between building dimensions and fortune. In modern design, treat it as a reference — not a constraint. Practical dimensions and comfortable daily use matter most.

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