Amateur Radio & Electronics Calculator Center
Interactive engineering calculators for amateur radio operators, electronics enthusiasts, students and experimenters. Calculate RF, antennas, SWR, transmission lines, capacitors, filters and electronic component values with graphical results.
SWR & Reflected Power
Calculate SWR from forward and reflected RF power and display the result using a visual SWR meter.
RF Power & Voltage
Calculate RF RMS voltage, current, peak voltage and peak-to-peak voltage.
Watts ↔ dBm Converter
Convert transmitter and signal power between watts and dBm.
Frequency & Wavelength
Calculate full-wave, half-wave and quarter-wave physical wavelength.
Half-Wave Dipole Designer
Calculate the approximate total and individual element lengths for a practical half-wave dipole antenna.
Quarter-Wave Vertical
Calculate a practical quarter-wave vertical radiator and radial length.
Coax Electrical Length
Calculate quarter-wave and half-wave coaxial transmission-line lengths using cable velocity factor.
RF Path Free-Space Loss
Estimate free-space path loss between two radio stations.
Capacitor Code Decoder
Decode common three-digit ceramic capacitor markings such as 104, 103 and 472.
Capacitive Reactance
Calculate capacitor reactance at any selected RF frequency.
LC Resonance Calculator
Calculate LC resonant frequency and display an approximate resonance curve.
RC Time Constant
Calculate capacitor charging time and display the capacitor charge curve.
RC Filter Calculator
Design a first-order low-pass or high-pass RC filter and view the approximate response.
Ohm's Law
Enter any two known electrical values to calculate the others.
4-Band Resistor Decoder
Select the colour bands and view the calculated resistance.
LED Series Resistor
Calculate the resistor and minimum resistor power required for an LED.
Voltage Divider
Calculate output voltage from a two-resistor voltage divider.