Shakkan-hō Pro — Professional unit conversion & aggregation app

Overview
Shakkan-hō Pro instantly converts between Japan's traditional shakkan-hō units and modern metric or imperial systems. Ideal for stoneworkers, builders, surveyors, farmers, real estate professionals and traders who need accurate, work-ready conversions and totals.

Who it's for
• Stone industry — calculate sai (才) ⇄ cubic meters, cubic shaku volumes, and manage tombstone and stone block dimensions; sum multiple stone sizes for estimates.
• Construction & architecture — convert ken, shaku, sun for drawings and precise measurements; convert tsubo ⇄ square meters for area planning.
• Real estate — compute land area in tsubo, tan, se, chobu and present clear metric equivalents for listings and valuations.
• Agriculture & forestry — manage fields in tan/are/chobu for yield estimates and subsidy paperwork.
• Trade & export — convert pounds, yards, barrels, gallons between US/UK systems and metric.
• Jewelry & precious metals — monme ⇄ grams, carat conversions and metal weight calculations.

Key features

Comprehensive unit coverage
Length: ri, cho, jō, ken, shaku, sun, bu, rin, mō ⇄ km, m, cm, mm ⇄ mile, yd, ft, in
Area: chōbu, tan, se, tsubo, gō ⇄ km², ha, a, m² ⇄ acre, yd², ft²
Weight: kan, kin, monme, fun, rin ⇄ ton, kg, g ⇄ lb, oz, grain (carat supported)
Volume: koku, to, shō, gō, sai, cubic-shaku ⇄ m³, L, mL ⇄ bbl, gal, qt, pt

Aggregate calculator
• Auto-sum multiple conversion results (e.g., combine several stone blocks’ sai)
• Keep historical calculations for quick reference
• Calculate required order quantities for materials

Dimension-based volume calculations
• Enter length × width × height in shakkan-hō to get m³ and sai
• Ideal for stone, timber and material volume estimates

Professional accuracy
• Up to 6 decimal places for high-precision needs
• Scientific notation for very large/small values
• Reliable for professional use

Usability
• One-tap copy of results
• Three adjustable font sizes
• Dark mode
• Supports 10 languages (Japanese, English, Simplified/Traditional Chinese, Korean, Spanish, German, Italian, French, Arabic)

Other benefits
• Fully offline — no internet required
• Lightweight and responsive UI
• Clear conversion tables for quick checks
• Secure local data storage only (no cloud sync by default)

Recommended users
Architects, carpenters, stonemasons, real estate agents, farmers, exporters, gemologists, antiques appraisers, traditional craftsmen, land surveyors, construction consultants.

Shakkan-hō Pro brings Japan’s traditional measurement systems into modern workflows — precise, fast, and tailored for professionals.