Electronics Calculator

Run the everyday electronics calculations in one place and get a clean table back. Ohm's law and the power wheel, resistor color codes both ways, the series resistor for an LED, voltage dividers, series and parallel networks, RC and RL time constants, reactance with LC resonance, and the running cost of a load. It is pure offline math with the Python standard library, so there is no API key, no rate limit, and nothing to break.

Values accept plain numbers, SI prefixes, and RKM notation. You can write 4700, 4.7k, 4k7, 100n, 2R2, 10mH, or 1M5 and each is read correctly.

What it calculates

Each calculation you pass has a type. These are the eight types and the fields each one reads.

ohms-law: give any two of voltage (V), current (A), resistance (Ω), power (W). It returns all four, so two knowns fill in the rest.

resistor-color-code: pass bands as a list of 3, 4, 5, or 6 colors to decode a resistor into its value and tolerance. Or pass a resistance and a bandCount (4 or 5) to encode a value into its color bands. Encoding also reads an optional toleranceColor (default gold).

led-resistor: give supplyVoltage, ledForwardVoltage, ledCurrentMa, and numberOfLeds in series. It returns the exact series resistor, the nearest E24 standard value, the power the resistor dissipates, and a suggested power rating.

voltage-divider: give vin, r1, and r2 for the output voltage and current. Add loadResistance to also see the loaded output.

component-network: give a componentType (resistor, capacitor, or inductor), a connection (series or parallel), and a values list. It applies the right rule for each, since capacitors add in parallel and resistors add in series.

rc-filter: give a resistance with either a capacitance (RC) or an inductance (RL). It returns the time constant, the 5-tau settling time, and the cutoff frequency.

reactance: give a frequency with a capacitance and/or an inductance for capacitive and inductive reactance. Give both L and C for the resonant frequency.

energy-cost: give power (or voltage and current) with a time as hours, or as hoursPerDay and days. Add an energyRate per kWh and a currency for the cost.

Every calculation takes an optional label that is copied to the output row so you can tell the rows apart.

Input

The input is a single calculations array. One object per calculation, any mix of types in one run. The default input holds one example of every type, so a run with no changes shows what each looks like.

{
  "calculations": [
    { "type": "ohms-law", "voltage": 12, "current": 0.5, "label": "12 V at 0.5 A" },
    { "type": "resistor-color-code", "bands": ["yellow", "violet", "red", "gold"] },
    { "type": "led-resistor", "supplyVoltage": 5, "ledForwardVoltage": 2.0, "ledCurrentMa": 20 },
    { "type": "rc-filter", "resistance": "10k", "capacitance": "100n" }
  ]
}

Output

One row per calculation. The overview table shows the type, your label, a short summary of the inputs, the headline answer, and a one-line result. Every row also carries the full set of numeric fields for that type, for example resistance, power, tolerancePercent, cutoffFrequency, resonantFrequency, or cost, plus a formatted version of each with its unit.

A calculation that cannot be solved, such as Ohm's law with only one value or an LED supply below the forward voltage, returns a row with ok set to false and a plain error message. One bad calculation never stops the rest of the run.

Example row for the LED resistor above:

{
  "calculationType": "led-resistor",
  "label": "",
  "result": "use 150 Ω (calc 150 Ω), dissipating 60 mW",
  "primaryFormatted": "150 Ω",
  "ok": true,
  "resistance": 150.0,
  "nearestStandard": 150.0,
  "resistorPower": 0.06,
  "recommendedPowerRating": 0.125,
  "actualCurrentMa": 20.0
}

Notes

The results are engineering calculations for design and study. Real parts carry tolerance, temperature drift, and parasitics, so treat the numbers as a starting point and check anything safety related against the component datasheets.