Calculating final tint after tinting over factory tint

[KWB]

Why did the math to to figure out the tent you have to do the rear window is 20% and you're adding on 25% tint you would do 0.20 x 0.25 =0.05% I'm not sure what the rear stock tint is but I asked a person at a tinting place and they said stock windows are 20%, if so that would make my back window 5%, but it's more like 15%, so I don't know if that's true about the stock window but that's how you do the math

[Bham]

2 hours ago, KWB said:

I have a 2006 Chevy Silverado 2500 I put 25% tint over the stock tint rear window and I believe it came out to look like the 15% tinted window

 

 

Even after doing this for 30years I still don't guess at what shade film is.  I always use a meter.  That being said, you also will not be able to tell exactly what the percentage is with just your eyes.  Especially with tint on top of factory tint.  The other part of your problem is that 25% is an odd number for tint and film off the roll can vary quite a few percentage points from what you are being told it is.  Factory glass also varies, so all these things make your math question,,, questionable because you don't have all the proper information.  

 

If it bothers you that bad, stop by a shop and ask them to put a meter on it.  

[Ryker]

KWB your windows will be much darker than just 15% if they put a 25 over factory.  As Bham says you can't tell with your eyes. My 20 will meter out about 17 on the front sides of your truck....