Long over due question about file size and work flow

When I go to edit a LR file in PS, I create an 8 bit TIFF. With my 5DII that generally results in a 130-180MB TIFF. Is that right? That seems big. But I've always just kind of let the apps do their things. Should I be changing anything to not have such massive files?

Sounds about right, welcome to the world of high resolution photo editing

Quick question though, why an 8bit and not a 16bit TIFF?

I don't think that sounds right at all! How many layers are in these tiff files?

No, that is the size of a 16 bit tif from the 5D2.

Easy way to figure it: 8 bits = 1 byte, 48 bits (16 bits x 3 channels) = 6 bytes. So 21 MP x 6 = 126.

More accurate way, because 1024 bytes = 1 KB and 1024 KB = 1 MB: 21MP x 6 /1.024 / 1.024 = 120.16 MB

tzalman's right. Doesn't matter what converter the Tiff was processed from, it's almost certainly going to be in the region of 120~126mb depending on how you count bytes.

On my mac it shows an 8-bit Tiff being 63.2mb and a 16-bit as 126.5, however, saving the 8-bit file as a layer results in a 125.8mb file, are you sure you're not accidentally saving the image as a layer?

If you open the image in Photoshop and it says "background" in the layers panel, then something's wrong, if it says something like "layer 0", it means you need to flatten the image.

OP goes from LR to PS, so the image will be a flattened tiff, 16bpc, ProPhotoRGB, without compression by default.

If you want to change any of that, go here:

I save the images with layers in case I ever want to reprocess. Makes it easy to go lower the opacity of a layer later, turn off a layer, etc. As far as 8 bit, I don't know should I be doing 16 bit tiffs?

If you're using ProPhotoRGB or do big (local) luminance / color edits in PS, I'd use 16bpc.
If you're using sRGB and don't do big (local) luminance / color edits in PS, I'd use 8bpc.

If you're using AdobeRGB, it's in between