Let’s be honest… window tint almost always makes a car look better, which is why tinted windows are such a popular aftermarket upgrade. Of course, window tint won’t just improve the look of your vehicle, it helps keep the inside temperature comfortable and also protects the interior from the sun’s rays.

So how dark is too dark for car window tinting?

The legal amount of tinting of any car window is measured by its light transmittance (LT), the amount of light that can pass through the tinted windows. Window tint laws ensure tinted car windows have a low enough light transmittance to allow for driver visibility. However the back windows can often be tinted darker than the front or even blacked out.

  • The front windscreen must let at least 75% of light through
  • The front side windows must let at least 70% of light through
  • Back passenger windows can be as dark as you want – these rules don’t apply

These rules however, don’t always stop car owners from unknowingly fitting aftermarket tints that are too dark to their front windows.

If you apply an aftermarket tint to your vehicle’s front windows you may be unknowingly breaking the law…

Most people are unaware that if they apply any measure of tint to the front windows of their car they are more than likely to be breaking the law. This is because most factory glass is in fact already supplied with a slight tint, usually around 13%, which would make the light transmittance 87% to begin with.

So, if you applied an ultra light film of say 30% (for 70% LT) to your 13% tinted glass, this would make your window’s light transmittance only 57% – this means you would be breaking the law…

What happens if you don’t comply with car window tinting laws?

It’s illegal to fit or sell glass that breaks the rules on tinted windows. It’s also illegal to sell a vehicle that breaks the laws of tinted car windows. Of course, you may find businesses selling window tint that exceeds regulations but don’t rely on the guy selling you aftermarket tint to tell you what’s legal. Before having your windows tinted, be sure to check with the laws about how dark your windows can be.

If you don’t follow the rules you may find yourself with a fine from the police. The police or Driver and Vehicle Standards Agency (DVSA) vehicle examiners use light measuring equipment to measure window tint and if they find your windscreen or front side windows to be tinted too much you could get:

  • a ‘prohibition notice’ stopping you using your vehicle on the road until you have the extra tint removed
  • a penalty notice or court summons

If you are considering vehicle window tinting, try to use a reputable window tinting specialist, buy good quality films and remember to stay within the law.

More details on car window tinting laws

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