Electro Master

Electro Master is a professional electrical calculator app for electricians, electrical engineers and students. Instant, accurate results — no internet connection required.

FREE CALCULATORS:

⚡ Ohm's Law — voltage, current, resistance and power. Fill any 2 values.
📉 Voltage Drop — drop in volts and percent, single and three-phase, with 3% / 5% warnings.
📏 Cable Size — cross-section from current, installation method, length and material.
🔐 Fuse / Breaker — protection size from power or current.
🔋 Power — active, apparent and reactive power.

ALSO FREE:
✓ Projects — notes, photos and a circuit list for every job
✓ Calculation history — reopen any calculation with its values
✓ Search across calculators, reference tables and projects
✓ Light and dark theme
✓ Works completely offline

PRO CALCULATORS:

Cables and installation
• Cable sizing to IEC 60364-5-52 — temperature and grouping derating, PVC/XLPE, up to 240 mm²
• Conduit fill — fill percentage and the smallest suitable conduit

Protection
• Loop impedance Zs — automatic disconnection for TN and TT, plus maximum cable length
• RCD selection — type, sensitivity, standing leakage and selectivity
• Selectivity — between breakers or gG fuses
• Short circuit current — Isc at the transformer

Motors and power
• DOL and star-delta starters
• Power factor correction
• Transformer, generator and UPS sizing

Solar
• PV string design — modules per string at cold and hot extremes, string fuses, DC cable
• Battery bank sizing

Plus grounding resistance and lighting (lux) calculators.

PRO ALSO INCLUDES:
✓ Offline reference tables — ampacity, AWG, wire colours, breaker curves, IP ratings and more
✓ Branded PDF reports with your company logo
✓ Circuit schedule — every calculation in a project exported as one PDF
✓ No ads
✓ Auto-renewing monthly subscription — cancel anytime

AVAILABLE IN 5 LANGUAGES:
🇬🇧 English | 🇧🇬 Bulgarian | 🇷🇴 Romanian | 🇷🇸 Serbian | 🇪🇸 Spanish

DISCLAIMER:
Calculations are for guidance only and do not replace the judgment of a qualified electrician. Verify results against the national edition of the applicable standard.