Electronics Calculators

Battery runtime estimate from capacity (mAh and volts, or Wh) and load (mA or W), with efficiency and usable depth of discharge.

Decibel conversions: power or voltage ratio to dB and back, and dBm to milliwatts and watts and back.

Series resistor for an LED from supply voltage, forward voltage and current, with nearest E12 and E24 values and real current.

555 timer calculator: astable frequency, period and duty cycle from R1, R2 and C, or monostable pulse width from R and C.

Ohm's law and power: give any two of voltage, current, resistance and power and get all four, with engineering units.

Energy use and running cost of a device from its watts, hours per day and electricity price: daily, monthly and yearly.

RC filter cutoff frequency, time constant and charge times to 63%, 90% and 99% from resistance and capacitance.

Decode 3 to 6 resistor color bands to ohms, tolerance and temperature coefficient, or encode a value into 4 or 5 bands.

Nearest standard E6, E12, E24, E48, E96 or E192 resistor values to a target, with the percent error of each neighbour.

Resistor voltage divider: output voltage, current and power from R1 and R2, or the R2 needed for a target output.

AWG copper wire: diameter, area and resistance per km, the nearest AWG for an area, and voltage drop over a run.