Surely there is some software that lets you draw a simple circuit diagram (DC voltage source and resistors) and then tell you the voltage, current, resistance, and power on R1, R2, R3, etc as well as totals.. instead of having to do it by hand, right?

The only things that seem to be able to do this that I've found so far are enterprise level software that look like they were designed in the 90's. Places like docircuits.com and circuitlab.com don't tell me the resistance total (for example in series-parallel circuits), or they would be decent.

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    \$\begingroup\$ Your keyword is 'spice'. \$\endgroup\$ Oct 16, 2012 at 8:50
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    \$\begingroup\$ I don't know any software that has a function to calculate the total resistance as such. The usual way to do it is to apply a fixed current source to the unknown load and then get the voltage as output (or vice versa). Then equivalent resistance is easily calculated. \$\endgroup\$
    – The Photon
    Oct 16, 2012 at 16:00

1 Answer 1


LTSpice (http://www.linear.com/designtools/software/) will easily do all that and more besides. You can build up the circuit, define your voltage sources and then measure power in all the components, and power being used by the voltage source. What you're after though is very basic with regards to analysis, so basically any Spice software will handle this. LTSpice is free, as is Tina, and many others. Certainly LTSpice has a great community around it, which sounds like it'll be useful (have a look at the LTSpice users group)

Also, if you want to find overall resistance, then you can find this from the voltage supplied and the overall current draw. For simple DC stuff you can take the values from Spice and bung them into a calculator, or you can do math with sources in LTSpice to be able to plot the resistance out over time for more complex AC analysis


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