A ballpark answer after a few minutes on Google told me that electric guitar strings are typically lower tension and are around 13-15 lbs *per string* That last part is important to remember. By comparison, an acoustic steel string guitar might be 20-25 lbs. Classicals come in much lighter at less than half of their steel counterparts so let's say 8-10 lbs per string.
These numbers are multiplied by six to give you the overall tension over six strings.
Now, let's talk Uke. Only four strings, and pretty light tension, let's say around 5-7 lbs each string.
That's a total of 20-30 lbs of total tension compared to Classical at 50-80, Steel string acoustic at 120-180 lbs, and electric guitar a bit lower at 75-90 lbs.
These are just general numbers. I haven't factored in scale length or string thickness. There are online charts and calculators to help you pick the right string for your instrument, string type, string diameter, and desired tension.
Here's a really good page from Daddario that explains string tension. They pretty much just focus on steel strings in this document.
http://www.daddario.com/Resources/JDCDAD/Videos/StringTension.pdf
This one's a bit more comprehensive:
http://www.daddario.com/upload/tension_chart_13934.pdf
I see cornfedgroove has also answered as I'm typing this. His numbers are pretty much what I expected to hear.
