Electrical Design Calc

A calculation toolbox for electricians and electrical designers, based on Japan's Indoor Wiring Code (JEAC 8001) and technical interpretations. Seven calculators with instant results — fully offline, works anywhere on site.

■ Voltage drop (free)
1φ2W / 1φ3W / 3φ3W simplified formulas (35.6/17.8/30.8). Drop rate, end voltage, pass/fail, plus the smallest conductor that passes.

■ Ampacity
IV/HIV wires (insulation × open/conduit × wire count × ambient correction) and CVT / CV-3C cables (in-air, 40°C base). JEAC 8001 §1340 tables built in.

■ Conduit sizing
6 conduit families (thin/thick steel, threadless, PF, CD, VE). Mixed wire sizes supported, and the total wire cross-section (incl. insulation) is always shown. 32%/48% fill toggle.

■ Cable tray width
MLIT Building Equipment Design Standard formulas (power single-layer / control stackable). CVT & CV-3C OD presets built in.

■ Pull box sizing
Straight/right-angle × wires/cables → W×L×D (rounded up to 50mm, depth by tier table).

■ Feeder & breaker selection
JEA Interpretation Art. 148: from ΣIM/ΣIH to required feeder ampacity, wire size, and breaker rating in one pass.

■ Messenger wire
Aerial cable tension with automatic wire selection (self-weight and wind included, SF 2.5 default).

■ History & per-site records (Pro)
Save results per construction site in one tap; export CSV (Excel-ready).

■ Pro (one-time purchase — not a subscription)
- Unlocks ampacity, conduit, tray, pull box, feeder and messenger calculators
- Calculation history with per-site records and CSV export
- No ads, even if added in the future

■ Official sources (government websites)
The public standards behind the calculations are published by Japanese government agencies:
- Technical standards interpretation for electrical installations (METI): https://www.meti.go.jp/policy/safety_security/industrial_safety/law/denjikokuji.html
- Building equipment design standards (MLIT): https://www.mlit.go.jp/gobuild/gobuild_tk2_000017.html

■ Disclaimer
This app is NOT an official app of METI, MLIT, or any other government agency, and is not affiliated with or endorsed by any government body. Results are reference values based on Japanese wiring standards. For actual design and installation, verify against the latest codes and specifications.

Recent changes:
Initial release.

- Voltage drop (1φ2W/1φ3W/3φ3W, pass/fail + smallest size) — free
- Ampacity (IV/HIV wires, CVT/CV-3C cables)
- Conduit sizing (6 families, cross-section total always shown)
- Cable tray width / pull box sizing
- Feeder & breaker selection (JEA Interpretation Art. 148)
- Messenger wire tension & auto selection
- Calculation history per site with CSV export (Pro)

Per Japan wiring code. Fully offline, no ads. Japanese/English/Chinese.