A **quarter-wave transformer** is a segment of transmission line used to match two different impedances. It works by transforming one impedance into another through a section exactly ¼ wavelength long (electrically).

The required characteristic impedance is calculated by: \[ Z_0 = \sqrt{Z_s \cdot Z_l} \] Where:

• Zₛ = source (transmitter or feedline) impedance
• Zₗ = load (antenna or device) impedance

If you specify a frequency and velocity factor, the calculator will also estimate the physical length of the ¼-wave transformer section: \[ \text{Length} = \frac{λ}{4} \cdot VF = \frac{300}{4f} \cdot VF \] This is useful for building matching stubs using coax or open wire line.