RF & Electronics Calculators
The bench math you reach for constantly — all in one place, all instant.
Ohm's Law & Power
Enter any two — the rest fill in.
dBm ↔ Watts
SWR ↔ Return Loss
LC Resonant Frequency
Decibels
Frequency ↔ Wavelength
Resistor Color Code (4-band)
Frequently asked questions
How do I convert dBm to watts?
Watts = 10^((dBm − 30) ÷ 10). So 30 dBm is 1 watt, 37 dBm is about 5 watts, and 60 dBm is 1000 watts. Type any value into the dBm↔watts calculator above for the instant conversion both ways.
What SWR is acceptable for ham radio?
Under 1.5:1 is excellent and 2:1 is still fine for most rigs; above 3:1 many transceivers fold back power to protect themselves. The SWR/return-loss calculator converts between SWR, return loss, and reflected power.
How do I calculate wavelength from frequency?
Wavelength in meters = 300 ÷ frequency-in-MHz. So 14 MHz is about 21 meters and 146 MHz is about 2 meters — which is where band names like “20 meters” and “2 meters” come from. The calculator does it for any frequency.
What is Ohm’s law?
Ohm’s law ties voltage, current, and resistance together: V = I × R, and power P = V × I. Enter any two values in the calculator above and it solves for the rest — handy for power supplies, dummy loads, and dropping resistors.