Approximating parts count on started reels

My method is not good if accuracy is an issue. Most of our reels come with a guage on the back. It is not a perfect count but with a good eye you can get within a couple hundred on reels of 5k. On the reels shipped with no guage I usually just hold a reel next to it and eyeball the guage, just make sure that you are using a reel from like parts (8x4, 12x4).

I also have placed marks on a table for some parts in increments of 50. I just stretch the tape out and count in 50's then count the rest individualy. This is more accurate that the gauge on the reels but you have to re-wind the tape back on the reel when your done.

Not the BEST ways, but they work for me....

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Ashok Dhawan, an old friend of SMTnet, says: Formula for counting components on SMT tape & reels [spiral belt]:

Length = Number of turns * 1/2 * 22/7 * ( dia outer + dia inner), where ...

Number of turns = ( dia outer - dia inner) / thickness of belt

So, Length = [1/2 * 22/7 * (dia outer^2 - (dia inner^2)]/ thickness of belt

It is assumed that belt is rolled tight - gaps between layers are negligible as compared to thickness of belt.

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