Quick answer
VLT, or visible light transmission, is the percentage of visible light that passes through a window. Lower numbers mean darker tint: 5% VLT lets through only 5% of visible light, while 70% VLT is close to clear. State tint laws are written in VLT, and a tint meter reads the glass and the film together.
Key takeaways
- VLT is the share of visible light a window lets through. Lower VLT means darker glass.
- Car glass isn't perfectly clear, so a tinted window reads darker than the film's rating.
- To estimate the total, multiply the two: 80% glass with 35% film comes out to about 28%.
- Officers use handheld meters that measure the whole window, glass and film together.
- Most states set different limits for the windshield, front side windows, rear side windows, and back glass.
What does VLT mean?
Visible light transmission (VLT) is the percentage of visible light that passes through a window. A window with 50% VLT lets through half of the visible light that hits it. A window with 5% VLT lets through only a twentieth.
It's easy to get backwards: the smaller the percentage, the darker the tint. When a state limits front side windows to 35% VLT, your windows need to let through at least 35% of visible light. A 20% film would be darker than the limit, not lighter.
Common tint percentages, compared
| VLT | How it looks | Where you usually see it |
|---|---|---|
| 70% and up | Close to clear, slight shade | Factory windshields and front side windows; clear UV and heat-rejecting films |
| 50% | Light tint, easy to see through | Drivers who want less heat and glare with a subtle look |
| 35% | Noticeably darker, still see-through in daylight | A front side window limit in a number of states |
| 20% | Dark, hard to see into from outside | Rear windows; front side windows in fewer states |
| 5% | Very dark, often called limo tint | Rear windows where allowed; exempt vehicles in some states |
Exact limits depend on your state and on the window. Your state page covers what applies where you live.
Why your tinted window is darker than the film's rating
Car glass isn't perfectly clear. Untinted side glass lets through most, but not all, visible light, and many SUVs and trucks come with darker factory privacy glass on the rear windows. When film goes on the glass, the two filter light one after the other, so their percentages multiply:
Total VLT = glass VLT × film VLT
- 35% film on 80% glass: 0.35 × 0.80 = 28% total
- 20% film on 75% glass: 0.20 × 0.75 = 15% total
- 5% film on 20% privacy glass: 0.05 × 0.20 = 1% total
That's why a tint shop may recommend a lighter film than the number in your state's law. A 35% film on typical factory glass can meter below 35%. Readings also vary a little from meter to meter, so good installers leave some margin.
How tint is measured at a traffic stop
Officers and inspection stations use handheld tint meters. The meter shines light through the window and measures how much reaches the other side, giving one VLT number for the glass and film together. Some states build a small measurement tolerance into the law, often around 3 percentage points.
If you have a medical exemption, a reading below the standard limit isn't a problem, as long as your tint is within what your exemption allows and you can show your documentation.
Why the limits differ by window
Most states set separate rules for the windshield, the front side windows, the rear side windows, and the back window. Front side windows usually have the strictest limits, because officers need to see the driver and drivers need a clear view of mirrors and traffic. Rear windows are often allowed to be much darker, sometimes with no limit, as long as the car has side mirrors on both sides.
Windshields are the most restricted. Many states only allow non-reflective tint above the AS-1 line, a mark near the top of the windshield, or within the top few inches. Many states also limit how reflective a film can be, separately from how dark it is.
Where medical exemptions fit in
A medical exemption lets a driver with a qualifying condition go darker than the standard limits, within whatever limits the state sets for exempt vehicles. The front side windows matter most here, since they're right next to the driver and usually have the strictest limits. Our complete guide to medical exemptions explains how it works.
If you think you may qualify, ShadedMD is the fastest way to find out: a 5-minute online questionnaire, a physician licensed in your state, one flat $129 fee with the best pricing of any online tint exemption service, and a 30-day money-back guarantee. See if you qualify.
Keep in mind that darker doesn't automatically mean more UV protection. Many nearly clear films block most UV. See does car window tint block UV rays? for the difference.
Frequently asked questions
Is 5% or 35% tint darker?
5% is much darker. VLT measures how much light gets through, so 5% VLT lets through only 5% of visible light, while 35% VLT lets through 35%.
What is limo tint?
Limo tint usually means 5% VLT film, the darkest film commonly used on cars. It's very hard to see into from outside, and in most states it isn't allowed on front side windows without an exemption.
Does factory glass count toward VLT?
Yes. A tint meter measures the whole window, so the glass and the film are counted together. Multiply the glass VLT by the film VLT to estimate the total.
How can I check my window tint percentage?
Many tint shops can measure your windows with a tint meter. Handheld meters are also sold online, though readings can vary slightly between devices.
Sources
- National Highway Traffic Safety Administration. Chief Counsel interpretation letter to Sun-Cool and Co. on FMVSS No. 205 light transmittance and aftermarket window tinting, 1990.
- Kentucky Legislative Research Commission. KRS 189.110, Unobstructed windshields, effective July 15, 2024.
- Texas Department of Public Safety. Window Tinting Standards, Vehicle Inspection.
- Virginia General Assembly, Legislative Information System. Code of Virginia section 46.2-1052, Tinting films, signs, decals, and stickers on windshields or windows.
- The Skin Cancer Foundation. UV Window Film and Tint.
This article is general information, not medical or legal advice. Tint laws change and differ by state, so check your state's current rules. Whether you qualify for an exemption is decided by a licensed physician based on your individual condition.
About ShadedMD
Medical tint exemptions you can trust
ShadedMD is an online medical window tint exemption service. Every questionnaire is reviewed by a physician licensed in your state, who approves or denies it based on medical need. ShadedMD offers the best pricing of any online tint exemption service: one flat fee of $129 with no add-ons, backed by a 30-day money-back guarantee. Physicians aim to complete reviews within 24 to 48 hours, and approved patients receive a signed certificate by email that they can download, print, and keep for one year.