Calculation reference
λ = c × VF / f; half-wave = λ/2; quarter-wave = λ/4.
Variables and units
λ is length in metres; c = 299,792,458 m/s; f is frequency in Hz (MHz × 1,000,000); VF is a dimensionless velocity factor.
Worked example
At 900 MHz in vacuum (VF = 1), λ = 0.333103 m, half-wave = 0.166551 m and quarter-wave = 0.083276 m.
Assumptions and limitations
VF = 1 gives free-space lengths. A lower VF models propagation in a medium. These are ideal electrical lengths, not finished antenna cut lengths: end effects, geometry and nearby objects require adjustment and measurement.
Reference: NIST SI definition of the speed of light. Cite this calculator using its permanent page URL and your access date.