Electrical calculators
Ohm’s law, watts/amps/volts conversions, 4- and 5-band resistor decoder, LED series-resistor sizing, and DC voltage drop over a wire run — the everyday quick-checks every hobbyist needs.
Electronics fundamentals
⚡Ohm’s law
V = I × R — solve any one from the other two.
🔋Watts / amps / volts
P = V × I for DC + single-phase AC, plus 3-phase.
🌈Resistor color code
4- or 5-band decoder + tolerance band.
💡LED series resistor
Resistor value from supply voltage, LED Vf + current.
🔌Capacitor charge / energy
Q, E, average current over charging time.
⏱️RC time constant
τ, V_charge/discharge over time, cut-off frequency.
Wiring & power systems
📏Voltage drop
DC voltage drop by gauge + length + current.
🧵Wire gauge (AWG)
AWG ↔ mm², ampacity, resistance per metre.
🔀Transformer turns
V₁/V₂ = N₁/N₂ = I₂/I₁ — step-up / step-down.
⚡Three-phase power
P = √3 × V_L × I × cosφ; star / delta conversion.
🔋Battery runtime
Hours from Ah / Wh + load + efficiency + DoD.
☀️Solar panel sizing
kW + panels + battery for daily kWh demand.