Dipole & Whip Antenna Length Calculator
Element lengths for half-wave dipoles, quarter-wave whips and 5/8-wave verticals at any frequency — with the 468/f cross-check.
Cut 2–3 % LONG and trim while watching SWR — height above ground, nearby objects and wire insulation all lower the resonant frequency, and wire is easier to shorten than lengthen. A quarter-wave whip only works against a decent ground plane: a car roof, or 4 radials sloped ~45° for a 50 Ω match.
Dipole Antenna Length Calculator computes cut lengths for half-wave dipoles, quarter-wave whips and 5/8-wave verticals — free, instant and private in your browser. Ham operators, LoRa/ISM tinkerers and students building their first wire antenna use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Dipole & Whip Antenna Length Calculator
Dipole Antenna Length Calculator computes cut lengths for half-wave dipoles, quarter-wave whips and 5/8-wave verticals using the standard engineering relation: λ = c/f, then L = 0.5λ·k (dipole) or 0.25λ·k (monopole), k ≈ 0.95 end-effect factor. Worked live: a 2 m-band (145 MHz) dipole is ~98 cm total — two 49 cm legs; the ham 468/f(MHz) feet rule gives the same answer. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Dipole & Whip Antenna Length Calculator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Dipole & Whip Antenna Length Calculator?
- ✓Implements the real formula — λ = c/f, then L = 0.5λ·k (dipole) or 0.25λ·k (monopole), k ≈ 0.95 end-effect factor — with the substitution shown, not a black box
- ✓Built for ham operators, LoRa/ISM tinkerers and students building their first wire antenna
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate dipole antenna length?+
Cut lengths for half-wave dipoles, quarter-wave whips and 5/8-wave verticals follows λ = c/f, then L = 0.5λ·k (dipole) or 0.25λ·k (monopole), k ≈ 0.95 end-effect factor. For example, a 2 m-band (145 MHz) dipole is ~98 cm total — two 49 cm legs; the ham 468/f(MHz) feet rule gives the same answer. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Why cut the antenna 5 % shorter than the free-space half wave?+
End effect: the wire's finite thickness and end capacitance make it electrically longer than its physical length. k ≈ 0.95 for thin wire (thicker elements need slightly more shortening). Practical builders cut 2–3 % LONG and trim to best SWR.
Does a quarter-wave whip work without a ground plane?+
Poorly — the missing half of the antenna is the image in the ground plane. A car roof, a chassis, or four λ/4 radials drooped ~45° complete it (the droop also raises the feed impedance toward 50 Ω). No plane → high SWR and detuned, inefficient radiation.
Is the Dipole Antenna Length Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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