Two Conductors in Parallel (Unbalanced) Above Ground Plane For D << d, h Z_{0}= (69/ε^{½}) log_{10}{(4h/d)[1+(2h/D)^{2}]^{½}} 
Single Conductor Above Ground Plane For d << h Z_{0}= (138/ε^{½}) log_{10}(4h/d) 
Two Conductors in Parallel (Balanced) Above Ground Plane For D << d, h_{1}, h_{2} Z_{0}= (276/ε^{½}) log_{10}{(2D/d)[1+(D/2h)^{2}]^{½}} 
Two Conductors in Parallel (Balanced) Different Heights Above Ground Plane For D << d, h_{1}, h_{2} Z_{0}= (276/ε^{½})log_{10}{(2D/d)[1+(D^{2}/4h_{1}h_{2})]^{½}} 
Single Conductor Between Parallel Ground Planes For d/h << 0.75 Z_{0}= (138/ε^{½}) log_{10}(4h/πd) 
Two Conductors in Parallel (Balanced) Between Parallel Ground Planes For d << D, h Z_{0}= (276/ε^{½}) log_{10}{[4h tanh(πD/2h)]/πd} 
Balanced Conductors Between Parallel Ground Planes For d << h Z_{0}= (276/ε^{½}) log_{10}(2h/πd) 
Two Conductors in Parallel (Balanced) of Unequal Diameters Z_{0}= (60/ε^{½}) cosh^{1} (N) N = ½[(4D^{2}/d_{1}d_{2})  (d_{1}/d_{2})  (d_{2}/d_{1})] 
Balanced 4Wire Array For d << D_{1}, D_{2} Z_{0}= (138/ε^{½}) log_{10}{(2D_{2}/d)[1+(D_{2}/D_{1})^{2}]^{½}} 
Two Conductors in Open Air Z_{0}= 276 log_{10}(2D/d) 
5Wire Array For d << D Z_{0}= (173/ε^{½}) log_{10}(D/0.933d) 
Single Conductor in Square Conductive Enclosure For d << D Z_{0}≈ [138 log_{10}(ρ) +6.482.34A0.48B0.12C]/ε^{½} A = (1+0.405ρ^{4})/(10.405ρ^{4}) B = (1+0.163ρ^{8})/(10.163ρ^{8}) C = (1+0.067ρ^{12})/(10.067ρ^{12}) ρ= D/d 
Air Coaxial Cable with Dielectric Supporting Wedge For d << D Z_{0}≈ [138 log_{10}(D/d)]/[1+(ε1)(θ/360)]^{½}) ε = wedge dielectric constant θ= wedge angle in degrees 
Two Conductors Inside Shield (sheath return) For d << D, h Z_{0}= (69/ε^{½}) log_{10}[(ν/2σ^{2})(1σ^{4})] ν = h/d σ = h/D 
Balanced Shielded Line For D>>d, h>>d Z_{0}= (276/ε^{½}) log_{10}{2ν[(1σ^{2})/(1+σ^{2})]} ν = h/d σ = h/D 

Two Conductors in Parallel (Unbalanced) Inside Rectangular Enclosure For d << D, h, w ∞ Z_{0}= (276/ε^{½}) {log_{10}[(4h tanh(πD/2h)/πd) ∑ log_{10}[(1+μ_{m}^{2})/(1ν_{m}^{2})]} ^{m=1} μ_{m}=sinh(πD/2h)/cosh(mπw/2h) ν_{m}=sinh(πD/2h)/sinh(mπw/2h) 