I just checked, both the Wire Wizard and the TCR Calculater deliver nearly the same values, so there shouldn't be that much of an difference. E.g. at the relative value of 1 is 2°F different and this trend continues. TCR: [QUOTE]"Temperature (degF)","Electrical Resistivity" -100,0.479572534158081 0,0.7857063375945039 70,1 200,1.2619670486383758 400,1.6691389293457468 600,2.067511360082879 800,2.436157185816745[/QUOTE] Wire Wizard: [QUOTE] "Temperature (degF)","Electrical Resistivity" -58,0.6118951675 68,1 212,1.2923387095 302,1.475302419 392,1.6631804436 482,1.8465909088 572,2.0247695849 800,2.4511648743 [/QUOTE]