Calculated using Onderdonk's Equation, which models the adiabatic heating of copper until it reaches its melting point (1083 °C).

$I = A \cdot \sqrt{ \frac{\log_{10}\left(\frac{\Delta T}{274 + T_{amb}} + 1\right)}{33 \cdot t} }$

Where:

• $I$ = Fusing current (Amps)
• $A$ = Trace cross-sectional area in circular mils (1 sq mil = 1.273 circular mils)
• $\Delta T = 1083 - T_{amb}$ (Temperature rise to melt copper)
• $t$ = Time duration of the current pulse (seconds)