Not compressed thickness, compressed volume.

The average gasket (not sure about Slant Sixes) is not a perfect circle, nor is it the bore diameter. So the compressed thickness takes all of that into account and gives you what really matters, the volume in its installed condition.

I think you all are splitting hairs here. .1 or .2 either way in a race motor isn't going to make much if any noticeable difference. There are a hundred different things in the car and engine that come into play that will make that .1 hard to measure. Sure we want a close idea and that is all the calculators are doing.
I'm pretty sure a Slant 6 head gasket opening is round. It definitely is not square

PS. Dennis, See what you started! Just go ahead and go to 12.5 to one! That will help!

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Bottom line is that when it's in the car and running I can say whatever number I want.

With a 5200 stall and 4.86 gears .1 or .2 of compression won't matter.

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Official Cookie and Mater Tormentor.

yea but to get the compressed volume one starts with the gasket diameter and the compressed thickness of the gasket and the formula shown below,

V=pi*radius squared*height

the online calculators use the diameter of the head gasket to get the radius and the compressed thickness of the head gasket to get the height, the compressed gasket volume is then just doing the math using the inputs.

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Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

That’s what I dun with my motor fer awhile… ‘til Howard measured stuff & set me straight…

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Rob

I’m Mater
The Kentucky Poser

The only number that matters is the MOV on the timeslip.

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Official Cookie and Mater Tormentor.

I said from the start that it won't make much difference.

But, why not use a more accurate number when it's available?