Electronics calculator
Resistor and capacitor codes, Ohm’s law, series and parallel, voltage dividers, LED resistors and RC time constants. Each one draws the part or the circuit as you type. Values accept engineering notation: 4k7, 100n, 2.2u, 12m.
Three-digit codes are in picofarads: the first two digits, then the number of zeros. 104 = 10 × 10⁴ pF = 100 nF. A letter at the end is the tolerance (J ±5%, K ±10%, M ±20%).
Fill in any two; the other two are calculated.
Resistors add in series and combine as 1/(1/R₁ + 1/R₂ + …) in parallel. Capacitors do the opposite.
Vout = Vin · R2 / (R1 + R2). Valid while the load draws much less current than the divider itself.
R = (Vsupply − Vf) / I. The nearest standard value above is suggested so the LED never gets more than you asked for. Check the datasheet for Vf.
τ = R · C. After one τ the capacitor reaches 63% of the supply, after 5τ about 99%. As a low-pass filter the cutoff is fc = 1 / (2π R C).
Everything is computed in your browser; nothing you type is sent or stored. Standard values follow the E12 / E24 series; colour codes follow IEC 60062. Always check a part’s datasheet before you build.