Utah Tint Laws
The darkness of window tint is measured by what is called Visible Light Transmission or VLT. In the state of Utah, VLT is measured by the net value. This means that in Utah VLT is the total amount of light allowed through the factory glass and any Window Tinting film applied to it, and not just the amount of light allowed through Window Tinting film alone.
According to Utah Tint Laws your front side windows, combined with aftermarket window tint must allow at least 43% VLT.
If you are using aftermarket window tinting film the State allows for up to a 2% variance which means that your VLT can be as low as 41%.
Utah tint law has no restrictions on how dark your window tint can be on any windows behind the driver.
Utah tint law does state that window tinting film cannot cover the third break light in back windshield.