Tinting Over Factory Tint Calculator
Enter the Visible Light Transmission percentage of your existing factory tint (e.g., 20 for 20%).
Enter the Visible Light Transmission percentage of the new tint film you plan to apply (e.g., 35 for 35%).
Combined VLT Result:
Understanding Visible Light Transmission (VLT) When Layering Window Tints
Many vehicle owners consider applying aftermarket window tint over their existing factory tint. This is often done to achieve a darker look, enhance privacy, or further improve heat and UV rejection. However, it's crucial to understand how Visible Light Transmission (VLT) works when layering tints, as the combined effect is not simply additive.
What is Visible Light Transmission (VLT)?
VLT is a measurement that indicates the percentage of visible light that passes through a window. For example, a window with 70% VLT allows 70% of visible light to pass through, meaning it blocks 30%. Conversely, a 5% VLT tint is very dark, allowing only 5% of light through and blocking 95%.
Factory tints, especially on rear windows and SUVs, typically range from 15% to 25% VLT. Aftermarket tints come in a wide range, from very light (e.g., 70%) to very dark (e.g., 5%).
How Layering Tints Affects VLT
When you apply a new tint film over an existing one, the light has to pass through both layers. This means that the VLTs multiply, rather than add up. Think of it this way: if your factory tint blocks 80% of light (20% VLT), and you apply a new tint that blocks 65% of the *remaining* light (35% VLT), the total light blocked will be significantly higher.
The formula for calculating combined VLT is:
Combined VLT = (Factory Tint VLT / 100) * (New Tint VLT / 100) * 100
This calculator helps you quickly determine the final VLT percentage, ensuring you meet legal requirements and achieve your desired aesthetic.
Why Calculate Combined VLT?
- Legal Compliance: Most regions have strict laws regarding the minimum VLT allowed for vehicle windows, especially on front side windows. Exceeding these limits can result in fines and require tint removal. Knowing the combined VLT helps you stay within legal boundaries.
- Safety: Extremely dark tints can impair visibility, particularly at night or in adverse weather conditions, posing a safety risk.
- Aesthetics: Achieve the exact level of darkness you desire without overdoing it or being disappointed by a tint that's not dark enough.
- Performance: While darker tints generally offer more heat and UV rejection, the specific film technology also plays a role. Understanding the final VLT helps manage expectations.
Examples of Combined VLT:
- Example 1: Moderate Darkening
- Factory Tint VLT: 20%
- New Tint VLT: 35%
- Calculation: (0.20 * 0.35) * 100 = 7.00% Combined VLT
- Result: This combination creates a very dark window, often below legal limits for front windows.
- Example 2: Slight Darkening
- Factory Tint VLT: 20%
- New Tint VLT: 50%
- Calculation: (0.20 * 0.50) * 100 = 10.00% Combined VLT
- Result: Still quite dark, but slightly lighter than the previous example.
- Example 3: Starting with Lighter Factory Tint
- Factory Tint VLT: 70% (common for front windows)
- New Tint VLT: 35%
- Calculation: (0.70 * 0.35) * 100 = 24.50% Combined VLT
- Result: This combination might be acceptable for front windows in some regions where 25% or 35% VLT is allowed.
Always check your local and state laws regarding window tint VLT limits before applying any film to ensure compliance and avoid potential issues.