Our ham radio calculator toolkit puts the everyday math on one page. Work out a wavelength, coax loss, what your SWR really costs, decibels and watts, Ohm’s law, LC resonance, S-meter readings, effective radiated power and battery runtime. Every answer updates as you type.
π Wavelength & Antenna Lengths
How long is a wave at this frequency?
βFull wavelength
βHalf-wave dipole
βQuarter-wave vertical
βBand
Antenna lengths use the common 468 / f and 234 / f formulas, which allow for end effect. Cut a little long and trim. For more antenna types, use the Antenna Length Calculator.
π Coax Loss
How much power reaches your antenna?
βLoss
βReaches the antenna
βPower lost
βLoss per 100 ft
Typical matched-line figures from manufacturer charts. High SWR adds more loss.
π SWR & Reflected Power
What does my SWR really cost me?
βReflected power
βMismatch loss
βReturn loss
βReflection coefficient
βSWR from your meter
βVerdict
π Decibels & Watts
Turn dB into “how many times more power.”
βPower ratio
βNew power
Every 3 dB doubles the power; 10 dB is ten times; 6 dB is one S-unit. 0 dBm = 1 milliwatt.
β‘ Ohm’s Law & Power
Fill in any two boxes. The rest are worked out.
βAnswer
E = I Γ RP = E Γ I
π LC Resonance
Fill in two of the three. Leave one blank.
βAnswer
βReactance at resonance
f = 1 Γ· (2Ο β(L Γ C)). Handy for traps, tuners and filters.
Check your radio’s manual for receive and transmit current. Cold weather can cut capacity by a third.
Which Ham Radio Calculator Do I Need?
Planning a new antenna run? Start with Coax Loss and Wavelength. Chasing a high reading on your meter? Use SWR to see how much power you really lose. Packing a go-kit? Battery Runtime tells you how long your radio will last. For the General and Extra exams, the dB, Ohm’s law and LC resonance calculators are great for checking your practice answers.
