How thick...

[mcnach]

Digital callipers here. Cost about £8-10 and work very well. I bought them precisely for that reason: what gauge strings do i have here? They do the job very well.
I may get sometimes slightly off readings (104 rather than 105 etc), but I think this is mostly due to angling the calliper etc. You must be perpendicular to the string.

[Dad3353]

[quote name='mcnach' timestamp='1373797998' post='2141622']...I may get sometimes slightly off readings (104 rather than 105 etc), but I think this is mostly due to angling the calliper etc. You must be perpendicular to the string.[/quote]
[pedantry]A false reading for this cause would always be superior (106 rather than 105 etc...), never a lower reading... [/pedantry]

[iiipopes]

Just a clarification for a post above: D'Addario Chrome Flatwounds are made with flat ribbon outer wrap. They are not ground, as are the half-wounds. Even then, the diameter or gauge listed for half-wounds is the resulting gauge after being ground down. To me, reading first few posts, the calipers are off, because D'Addario has very tight quality control.

[steve-soar]

[quote name='mcnach' timestamp='1373797998' post='2141622']
Digital callipers here. Cost about £8-10 and work very well. I bought them precisely for that reason: what gauge strings do i have here? They do the job very well.
I may get sometimes slightly off readings (104 rather than 105 etc), but I think this is mostly due to angling the calliper etc. You must be perpendicular to the string.
[/quote]
I remember doing my Engineering O Level, back in 1982, and our teacher came in one day with a digital micrometre from Rolls Royce. He told us that to buy one like this would cost over £200!!!

[cameltoe]

[quote name='KingBollock' timestamp='1373323241' post='2136301']
I wish I hadn't done that now, I'm a little disappointed... Having said that, I don't know what to be disappointed in, I don't know which is wrong, the callipers or the strings.

[font=courier new,courier,monospace]The strings are: .105 .085 .070 .050[/font]
[font=courier new,courier,monospace]And I got:[color=#fff0f5]......[/color] .103 .083 .067 .048[/font]

The strings are D'Addario Chromes.

I'd test other strings but they're the only ones I even know the make of , nevermind the gauge.
[/quote]

Is there a way to calibrate the calipers? Seems like the base setting is off, as the readings are consistent. Like you would on scales, for instance, to make sure they read 0.00 before anything is placed on them.

[KingBollock]

[quote name='cameltoe' timestamp='1373911582' post='2143057']
Is there a way to calibrate the calipers? Seems like the base setting is off, as the readings are consistent. Like you would on scales, for instance, to make sure they read 0.00 before anything is placed on them.
[/quote]
Yup, there's a zero button. You can zero it at any point along its length, but before I take each measurement I close the callipers fully and press the zero button to bring it to a flat zero.

[JapanAxe]

I use digital digital calipers to measure string diameter on both guitar and bass. They are close enough that you can tell what gauge the string is supposed to be.

[Telebass]

I have a good cheap digital caliper and an old Moore & Wright imperial micrometer.
Whilst the calipers have much more general utility, the mike, properly set for zero, is still what I prefer for string measurements.