Tools

Each calculator shows the formula, the parameters it uses, a worked example, and the checks it applies.

• Battery Life Calculator

  Estimate run-time from battery capacity in mAh, average load current and an optional derating factor.

• Capacitor Calculator

  Capacitive reactance Xc at a frequency and RC time constant τ from resistance and capacitance.

• Resistor Color Code Decoder

  Decode 4-, 5- and 6-band through-hole resistor colour codes to resistance, tolerance and optional TCR.

• LED Series Resistor Calculator

  Size the series resistor for one LED string from supply voltage, forward voltage and current, then pick a nearby E-series value and check resistor power.

• Ohm's Law Calculator

  Solve V = I × R for voltage, current or resistance when you know the other two.

• Parallel Resistor Calculator

  Combine resistors in parallel or series. See the equivalent resistance and the conductance of the network.

• Electrical Power Calculator

  Compute DC power and the third quantity from any two of voltage, current and resistance using P = VI, I²R and V²/R.

• Reactance Calculator

  Capacitive Xc and inductive Xl from frequency and capacitance or inductance.

• Electronics Unit Converter

  Convert resistance, voltage, current, capacitance, inductance, frequency, time, power and energy with SI prefixes.

• Voltage Divider Calculator

  Find the tap voltage of a two-resistor divider, see how a load pulls that tap down, and check the current and power in each resistor.