, where:

T_{f} = Film Temperature (K)

T_{s} = Surface Temperature (K)

= Surrounding Temperature (K)

The efficiency of a fin, which should not be confused with the fin effectiveness, is defined and can be graphed as:

, where:

= Fin Efficiency (%)

h_{f} = Convection Coefficient of Fin (W/(m^{2}*K))

k = Thermal Conductivity of Fin (W/(m*K))

t_{f} = Thickness of Fin (m)

, where:

Gr = Grashof Number

g = Gravity (m/s^{2})

= Coefficient of Thermal Expansion (1/K)

T_{s} = Surface Temperature (K)

= Bulk Temperature (K)

, where:

= Rate of Heat Lost (W)

T_{hs} = Temperature at base of heat sink (K)

R_{hs} = Thermal Resistance of Heat Sink (K/W)

, where:

h = Heat Transfer Coefficient (W/(m^{2}*K))

q = Flow of Heat (W)

A = Cross-Sectional Area (m^{2})

T = Difference in temperature (K)