📏 Lỗ Ban Ruler
The carpenter's feng-shui ruler on your screen: type or drag any measurement and see it land on all three Lỗ Ban scales at once — 52.2 cm for door openings, 42.9 cm for furniture and solid blocks, 38.8 cm for altars and grave work — each zone named, judged lucky or unlucky, with the nearest lucky range suggested.
👆 Drag on the ruler to slide the red line — or type the number. Each band shows one full cycle of that scale; the measurement wraps around it.
📖 How the three scales are used
For the CLEAR opening where air and light pass: door and window openings measured inside the frame. 8 zones × 65.25 mm.
For SOLID built things of the living: furniture, beds, kitchen counters, steps, sills — measured over the solid block. 8 zones × 53.625 mm, each with 4 named sub-zones.
For what belongs to the ancestors: altars, ancestral tablets, graves and tombs. 10 zones × 38.8 mm.
📏 The Lỗ Ban ruler is carpentry folklore named after the legendary Chinese master builder — a tradition of auspicious dimensions, not physics. Build to code first; let the lucky millimetres come second.