Free ham radio calculators & tools
Free calculators, references and finders. No account needed.
Build an antenna
Lengths, coils, chokes and filters.
Antenna calculatorDipole, vertical, EFHW and more, in feet or metres Coil calculatorAir-core inductors, with 3D-printable coil forms Choke & balun designerPick a toroid, turns and wire for your bands and power Choke estimatorSee what the core and coax you already have will do Bandpass filterComponent values and coil specs for any bandFeed line & power
What actually reaches the antenna.
Coax lossLoss for RG-58, LMR-400 and more at any frequency ERP calculatorEffective radiated power, incl. 60m, 630m and 2200m limits Band planUS allocations by license classFind & buy
Repeaters, radios and prices.
Repeaters near youSearch by city or ZIP, with offsets and tones Radio finderFilter by bands, budget and features, or take the quiz Price trackerCurrent prices across the big ham dealers 3D-printable gearFree STL files, plus a filament guide for antenna parts HamfestsSwap meets and hamfests near youGet on the air
Who's on, and where to point.
Callsign lookupLicense, grid and who's hearing them Satellite passesLive positions and passes over your grid POTA mapActivators on the air right now Compare stationsYour FT8 signal against others in your grid Contest calendarContests on now and coming up HamClockFull-screen shack clock and mapQuick calculators
Frequency to wavelength
Enter a frequency
Half-wave dipole length
Enter a frequency
Quarter-wave vertical
Enter a frequency
Distance between grids
Enter two grid squares
Where to start
Every tool here runs in your browser, free and with no account. A few common starting points:
- Building a first wire antenna? Get cut lengths from the dipole and vertical antenna calculator, then read our dipole antenna guide.
- Choosing feed line? The coax loss calculator shows how much power each cable type loses over your run. Loss grows with frequency and length.
- RF in the shack or on your audio? Design a common-mode choke with the choke and balun designer, and see troubleshooting RFI.
- Homebrewing? The bandpass filter calculator and air-core coil calculator give component values, and the ERP calculator works out your effective radiated power.
- Not sure where you can transmit? Check the US band plan by license class.
- Just licensed? Find repeaters near you and make your first contact.