Mực Thước – Luban Ruler
Android · Free · No account · iOS version in development
A Luban ruler for the person holding the tape: pick the item, enter the size, and see at once whether it is good, how many millimetres it sits from the section edge, and the nearest good size.
The app is in Vietnamese today. English and Chinese versions are on the way.
Features
A measuring tool for the home that explains every number instead of only painting it red or black.
The right ruler for each item
Doors and openings are measured clear (inside the frame) on the 52.2 cm ruler. Furniture and masonry are measured overall on the 42.9 cm ruler. Altars and graves use the 38.8 cm ruler. You pick the item; the app picks the ruler.
A verdict with its margin
Good, good but near the edge, or bad, with the section and sub-section names and the millimetres left to the section edge. Every verdict has a word and a symbol, never color alone.
Nearest good size
For a bad size, the app suggests the nearest good size below and above. The “Good ▶” button jumps to the next good size, rounded to the step you choose.
Width × height grid
A door needs both its width and its height to be good. The grid shows every pair around your size in 5 to 50 mm steps, plus the closest pairs where both pass.
Projects for the whole house
Save each item by area, such as Ground floor or Altar room, add a photo if you like, and share the list with your builder through any messaging app.
Choose the ruler your source uses
Sources disagree: 52.2 or 52 cm, 38.8 or 39 cm. Choose in Settings and saved results are recalculated. The near-edge tolerance and rounding step are adjustable too.
No account, data stays on the phone
Projects and photos are stored only on your phone. The ruler works offline, up to 50 m.
The three Luban rulers used in Vietnam
Each ruler is divided into good (red) and bad (black) sections that repeat in a cycle. The item decides which ruler to use and how to measure.
| Ruler | Cycle | Used for | Measure | Good (red) | Bad (black) |
|---|---|---|---|---|---|
| Thông thủy 52.2 cm | 522 mm, 8 sections | Doors, windows, gates, garage doors, light wells, vents | Clear opening | Quý Nhân, Thiên Tài, Nhân Lộc, Tể Tướng | Hiểm Họa, Thiên Tai, Cô Độc, Thiên Tặc |
| Dương trạch 42.9 cm (文公尺) | 429 mm, 8 sections | Kitchen counters, beds, cabinets, tables, stair steps, masonry | Overall | Tài 財, Nghĩa 義, Quan 官, Bản 本 | Bệnh 病, Ly 離, Kiếp 劫, Hại 害 |
| Âm phần 38.8 cm (丁蘭尺) | 388 mm, 10 sections | Altars, altar cabinets, God of Wealth altars, graves | Overall | Đinh 丁, Vượng 旺, Nghĩa 義, Quan 官, Hưng 興, Tài 財 | Hại 害, Khổ 苦, Tử 死, Thất 失 |
How it works: subtract whole cycles from the size and see which section the remainder falls in. A main door 1260 mm wide on the 52.2 cm ruler: 1260 − 2 × 522 = 216 mm, inside Thiên Tài (195.75–261 mm), so it is good. The nearest bad edge is at 195.75 mm, 20.25 mm away.
Clear opening is the open space inside the frame, without the door leaf or frame. Overall is the outermost size of the object.
FAQ
What is a Luban ruler?
A Luban ruler (thước Lỗ Ban, 魯班尺) is a folk measuring tape used to choose sizes for houses, furniture and altars. It is named after Lu Ban, the patron of carpenters. Each ruler is divided into good (red) and bad (black) sections that repeat in a cycle. Vietnam commonly uses three: 52.2 cm, 42.9 cm and 38.8 cm.
Which ruler should I use for a door?
The 52.2 cm thông thủy ruler, measured as a clear opening: the open space inside the door frame, without the leaf. Check both width and height. Mực Thước shows “2/2” when both are good, and the width × height grid finds pairs where both pass.
Which ruler should I use for an altar?
The 38.8 cm âm phần ruler (丁蘭尺, Đinh Lan), measured overall: the outermost size of the altar. Check width, depth and height.
Why do websites and apps give different results?
Because sources disagree: the clear-opening ruler is given as 52.2 or 52 cm, the altar ruler as 38.8 or 39 cm, and some use the 38.8 cm ruler for all furniture. Many common sizes also sit close to a section edge, so a few millimetres change the verdict. Mực Thước names the ruler behind every result, lets you choose the variant in Settings, and flags “near the edge” when a size is closer than your tolerance.
Is it free?
The app and the ruler are free, with 1 project. A one-time Google Play purchase unlocks unlimited projects and removes ads, or you can buy ad removal alone. The free version shows one small banner on the project list. It never covers the ruler or the verdict.
Does it need an internet connection or an account?
No account is needed. The ruler and projects work offline. The network is only used to load ads and for Google Play purchases.
Does it replace building codes?
No. The Luban ruler is a custom for reference. Door, stair and railing sizes must still follow building codes and engineering advice.
Feedback & Support
Does a result disagree with your tape, or is an item missing? Write to us.