Electrocal is an app that is designed well to help electronics engineers and electronics hobbyist in designing electronics circuits.
The app contains the following calculators.




Color coded resistor calculator

Resistance calculator

Series resistors calculator

Parallel resistors calculator

Series capacitors calculator

Parallel capacitors calculator

Capacitance of a capacitor calculator

Parallel plate capacitor calculator

Capacitive reactance calculator

Ceramic capacitor calculator

Polyester capacitor calculator

Surface mounted capacitor (SMD) calculator

Toroidal inductor winding calculator

Indutor winding calculator

Air core inductor winding calculator

Adjustable voltage regulator calculator

Zener diode voltage regulator calculator

Bipolar junction transistor (BJT) amplifier analysis calculator

LR filter calculator

Parallel RLC calculator

Transformer winding calculator

555 timer astable multivibrator calculator

555 timer monostable multivibrator calculator

Op-amp inverting amplifier calculator

Op-amp noninverting amplifier calculator

Op-amp difference amplifier calculator

Sallen-Key single-pole filter calculator

Sallen-Key double-pole filter calculator

Butterworth passive filter calculator

Chebychev passive filter calculator

Bessel passive filter calculator

Active filter calculator

RC passive filter calculator

Inductive reactance calculator

Series LRC circuit calculator

Resistor voltage divider calculator

Wheatstone bridge calculator

Charging/Discharging a capacitor calculator

Charging/Discharging an inductor calculator

Resistivity calculator

PCB trace width calculator

Attenuators calculator

Microstrip calculator

Wave guide calculator

Electrical power calculator

Decibel calculator

Alternating current (AC) calculator

Ohms law calculator

Deltar -> Star calculator

Star->Deltar calculator

Multi layered air core inductor design

Spiral inductor design

and many more calculator