How to calculate the VLT of window tint once applied

Car window tinting films are measured in visible light transmission (VLT) levels, which is measured as percentage. So when you see a window tint being referred to as a percentage, this is the VLT, e.g. our 20% dark smoke film has a VLT of 20%.

So what does the percentage actually mean? In simple terms, the VLT is the percentage of light that the film allows to pass through. So a 5% VLT film is very dark as it only lets though 5% of visible light and a 70% film is very light as it lets through 70%.

However, this doesn’t mean that when you apply a 5% tint to your car window it will only allow 5% of light through. The glass in car windows already has a slight tint to it of around 80%.

To calculate the actual VLT of the glass with film applied to it, you need to mutiply the VLT of the window tint applied by the VLT of the glass. E.g applying a 5% film to glass with an 80% tint to it, you would multiply 5% x 80% = (0.05×0.80)x100 = 4%. So the glass and window tint would have a combined VLT of 4%.