i was wondering how much square ft it would take to do the whole inside of an rx8 if anyone has done it (dynamat, fatmat...dosent matter just want to know sqare footage)

 

The whole inside? Door panels? Roof? Tail lights to firewall? I'd say 100sqft easy. Probably more like 125sqft. 40sqft got me the trunk area and some behind the rear seats over the gas tank. Also keep in mind that's still only one layer. So it DOES matter which sound deadener you use. Some of the cheaper brands are half the thickness, and sometimes therefore, half as effective. If you're going to put all that labor in, you want the best possible outcome. Just keep that in mind while shopping.

 

I used B-Quiet on my 2008 G35S...worked great - two rolls for entire interior, doors, trunk and wheel wells...

 

It depends how much you want to cover. Depending what you use, you're talking up to a pound per square foot, which starts getting heavy. My goal was to knock down drone and kill panel resonance without adding too much weight. I used Second Skin Damplifier which is 1/3 lb/sq ft, comes in easy to work with 1x2' panels, is butyl rubber (no tar) and self-sticks. There's a fair amount of factory installed damping and I didn't cover that. The trunk area is solidly covered otherwise, and the stuff under the passenager seats. I covered the transmission tunnel well, the rest of the interior with what made sense. The tally so far:
Trunk lid = 6; Rear deck = 5; Trunk = 28; Roof (important!) = 4; Interior = 20; Total = 63 square feet. I have yet to do the inside of the doors, but I'll guess the final total will be around 80.

It's the first car I've done this with, but I'll still say it's a big PIA project, unless you're sloppy, drunk, fast, or experienced.