Skip to main content

​
What do the nanometer numbers on blue light glasses mean?

By Spektrum Glasses Editorial Team · Published 2026-08-07 · Updated 2026-08-07 · Facts re-checked 2026-08-07 How this page is written and checked: our editorial method · how we verify claims

​
Short answer

A nanometer (nm) is the unit used for the wavelength of light. Visible light spans roughly 380 to 780 nm, and blue light occupies about 400 to 500 nm of that. Because a lens filters every wavelength by a different amount, any blue-light percentage is meaningless unless it names the wavelength band it was measured across.
  • Nanometers measure wavelength; blue light sits at roughly 400-500 nm.
  • Filtering varies steeply within the band, so one percentage cannot describe a lens.
  • Our clear lens: 99.99% filtered at 400 nm but only 33.1% at 450 nm.
  • A near-clear lens cannot filter the whole blue band without adding visible tint.
  • Evidence for symptom benefit is limited and contested; the numbers describe glass, not outcomes.

​
What a nanometer actually measures

Light travels as a wave, and a nanometer (one billionth of a meter) is the unit used to describe the length of that wave. Wavelength determines the color you see and the energy each photon carries: shorter wavelengths carry more energy per photon than longer ones. The rough landmarks are worth memorizing, because every honest lens spec is written in them:
  • Below 280 nm: UVC, absorbed by the atmosphere, not a practical concern at ground level.
  • 280-315 nm: UVB.
  • 315-400 nm: UVA.
  • 400-500 nm: the blue band. This is what people mean by “blue light”.
  • 500-580 nm: green, where the eye is most sensitive in daylight conditions.
  • 580-780 nm: yellow, orange, red.
A lens does not treat this range as one thing. Its filtering is a curve across wavelength, not a single value, and the curve can fall very steeply. That single fact is why the nanometer numbers on a spec sheet matter more than the headline percentage printed on a box.

​
The bands inside blue light are not interchangeable

“Blue light” is a 100 nm-wide range, and different parts of it are discussed for different reasons. When a brand names a band, it is telling you which conversation it is entering. The practical consequence: a lens optimized around 400-420 nm and a lens optimized around 460-480 nm are different products with different tints, even though both can be described as “blue light glasses”. A number quoted from one band says nothing about performance in the other.

​
Why a percentage without a wavelength tells you nothing

Here is our own clear lens, measured by COLTS Laboratories (report O-SPG111015, spectral transmittance per ANSI Z80.3): One lens. Four numbers, spanning 99.99% down to 33.1%, across a 50 nm stretch. UVA and UVB are both filtered above 99.99%, and photopic (visible) transmission is 91.6%, meaning the lens is near-clear with no heavy tint. Now consider how that data could be marketed. “Blocks 99.99% of blue light” is technically traceable to the 400 nm figure and still leaves a buyer badly misinformed, because the same lens passes roughly two-thirds of the light at 450 nm. “Blocks 33%” is equally incomplete in the other direction. Neither sentence is usable without the wavelength attached. This is the single most common failure on blue light glasses packaging: a peak value from the steepest part of the curve, presented as if it described the whole band. When you see a bare percentage, assume it came from the most flattering wavelength available until the seller shows you otherwise.

​
The trade-off: filtering the whole band costs you clarity

Blue light is visible. Removing most of it removes a visible color, so the lens necessarily takes on a yellow, amber, orange, or red cast. There is no way around this, and any lens described as both fully clear and a near-total blue filter is describing something that does not exist. Our own range shows the trade-off across four points, all measured with the band stated:
  • Clear lens: 91.6% visible transmission, but filtering falls to 33.1% by 450 nm.
  • ZENOX clear lens: about 52% average across the blue band, 100% of UV. Still clear-looking, still cannot cover the whole band.
  • Amber evening lens: 97.9% across 400-500 nm, 99.9% of HEV, 98.3% across the 460-480 nm region. Visibly amber.
  • Orange lens: 99.96% across 380-500 nm. Red lens: 99.83% across the same span. Both measured in 2026 by our lens manufacturer’s optical laboratory.
The orange and red lenses are not suitable for driving. Removing that much of the short-wavelength range distorts color perception, including the appearance of traffic signals and brake lights. Choose the tint by when and where you intend to wear it, not by which number is largest.

​
What the numbers do not tell you

A transmittance curve is a measurement of glass and coating. It describes the lens, not the person wearing it, and it should not be read as a claim about how anyone will feel. The published work here is thinner than marketing implies. Leung, Li and Kee (PLOS ONE, 2017) measured commercially available blue-light-filtering lenses and found they reduced the calculated blue-light hazard by roughly 10 to 24 percent. That figure is a weighted photobiological index computed from a spectrum, not an observed outcome in a wearer. Evidence for symptom benefit is limited and contested, and a lens spec sheet cannot settle it in either direction. Two further points of context. First, outdoor daylight contains far more short-wavelength energy than any screen, so a percentage measured against a lamp or a monitor is not a statement about total daily exposure. Second, screen time affects people through blink rate, viewing distance, posture, and hours of use, none of which a lens changes. Our position is that the measurement should be published in full and the interpretation left honest. That is why the raw numbers, the band, the lab, and the report number are all on this site.

​
How to read a lens spec sheet

When you are comparing lenses, five questions separate a measurement from a marketing number:
  1. Which band? A percentage must name the wavelengths it covers: “97.9% across 400-500 nm”, not “blocks 98%”. If the band is missing, the number is unusable.
  2. A point or an average? “99.99% at 400 nm” is a single wavelength. “99.96% across 380-500 nm” is an average over a span. The second is far harder to achieve and far more informative.
  3. Who measured it? Look for an independent laboratory accredited to ISO/IEC 17025, ideally by a recognized accreditor such as A2LA, and a report number you can reference. Our clear and amber lenses were measured by COLTS Laboratories under report O-SPG111015 (A2LA certificate 1612.01).
  4. Under which method? Spectral transmittance for non-prescription eyewear is measured per ANSI Z80.3. Naming the standard tells you the test was not improvised.
  5. What is the visible transmission? A lens that filters heavily in the blue band will have lower photopic transmission and a visible tint. Our clear lens is 91.6%. If a seller quotes deep blue filtering and claims no tint, the two figures are in conflict.
If a product page answers all five, you can compare it fairly against any other. If it answers none, the percentage on the box is a slogan.

​
Where these numbers come from

Every measured figure quoted here is transcribed from a third-party laboratory report, published in full with the wavelength band and the report number: lab results. Our rule for what may appear on this page at all is on how we choose what to publish.