What wavelengths count as blue light?
By Spektrum Glasses Editorial Team · Published 2026-08-05 · Updated 2026-08-06 · Facts re-checked 2026-08-06 How this page is written and checked: our editorial method · how we verify claimsShort answer
Blue light is the shortest-wavelength band of visible light, conventionally 400 to 500 nanometers, sitting between ultraviolet below 400 nm and green above 500 nm. Some definitions start at 380 nm and fold in violet. Within the band, 400-450 nm is often called high-energy visible, and roughly 460-480 nm is where human circadian signaling is most sensitive.- Blue light is conventionally 400-500 nm; some definitions start at 380 nm.
- No standards body fixes one universal blue-light boundary, so bands vary by source.
- A filtering percentage without a stated wavelength band is uninterpretable.
- Our clear lens filters 99.99% at 400 nm but 33.1% at 450 nm.
- Filtering the whole 400-500 nm band requires a visible tint; clear lenses cannot.
Where blue sits in the visible spectrum
Visible light runs roughly 380 to 780 nanometers. Blue occupies the short-wavelength end of that range, conventionally 400 to 500 nm, with ultraviolet immediately below it and green immediately above. A nanometer is a billionth of a meter, and the number describes the physical length of one wave cycle. Shorter wavelength means more energy per photon. The relationship is exact: photon energy in electron volts equals 1240 divided by the wavelength in nanometers. So a 400 nm photon carries about 3.10 eV, a 450 nm photon about 2.76 eV, and a 700 nm red photon about 1.77 eV. Blue photons are therefore roughly 1.5 to 1.8 times as energetic as red ones. This energy difference is the entire physical basis for treating blue as a distinct band, and it is also the reason “high-energy visible” and “blue light” are often used interchangeably even though they are not quite the same range. The boundaries are conventions, not laws of physics. The spectrum is continuous. Nothing changes abruptly at 400 nm or at 500 nm, and different fields draw the lines in different places for their own reasons.The sub-bands inside 400 to 500 nm
Because 400-500 nm behaves quite differently at its two ends, it is usually broken into narrower bands. There is no single authority that fixes these divisions, so ranges you see quoted elsewhere may differ by 10 or 15 nm in either direction.
Two details matter when comparing specs. First, optical-safety weighting functions used to calculate blue-light hazard do not peak at 400 nm; they peak in the 430-440 nm region, so a lens that filters aggressively at 400-410 nm and lightly at 435 nm scores worse than its headline number suggests. Second, the 460-480 nm circadian band sits at the long end, where filtering starts to cost visible color neutrality. Those two facts pull lens design in opposite directions.
Why a percentage is meaningless without a band
A filtering figure is a number over an interval. Change the interval and the number changes, often dramatically, with no change to the lens. Our clear lens was measured by COLTS Laboratories (report O-SPG111015), an A2LA-accredited laboratory operating to ISO/IEC 17025 under accreditation certificate 1612.01, with spectral transmittance run per ANSI Z80.3. The point measurements are:- 400 nm: 99.99% filtered
- 410 nm: 95.1% filtered
- 420 nm: 63.0% filtered
- 450 nm: 33.1% filtered
- Visible (photopic) transmission: 91.6%
- UVA and UVB: both filtered above 99.99%
What a clear lens can reach and what it cannot
There is a hard physical constraint here, and it is worth stating plainly. Light between roughly 450 and 500 nm is light the eye actually sees as blue. Removing most of it necessarily removes a visible part of the spectrum, which is why any lens that filters heavily across the full 400-500 nm band looks yellow, amber, orange, or red. A near-clear lens with 91.6% photopic transmission cannot filter the long end of the blue band, because doing so would stop it being near-clear. This is optics, not product positioning. Tinted lenses reach where clear ones cannot. On the same COLTS report, our amber evening lens filters 97.9% across 400-500 nm, over 98% of the blue band, 99.9% of HEV, and 98.3% at the 460-480 nm circadian band. Our orange lens measures 99.96% across 380-500 nm and the red lens 99.83%, both measured in 2026 by our lens manufacturer’s optical laboratory. Neither the orange nor the red lens is suitable for driving: at that level of filtration, color discrimination and total light transmission are both substantially reduced. On what any of this does for a person, be careful. Leung, Li and Kee (PLOS ONE, 2017) found that commercially available blue-light-filtering lenses reduced calculated blue-light hazard by roughly 10-24%. That is an optical calculation, not a clinical outcome. The evidence for downstream symptom or circadian benefit is limited and contested, and any product promising a symptom outcome is promising something the measurements do not support. Filtration figures describe the lens. They do not describe you.Where blue-band light actually comes from
Daylight is overwhelmingly the largest source. Outdoor illuminance on an overcast day is on the order of 10,000 lux at the eye and clear midday sun is far higher, while a computer monitor at desk distance contributes on the order of 100 lux. These are typical ranges rather than measurements of any specific setup, but the ratio is not close. For anyone who goes outside at all, screens are a minor share of daily blue-band exposure. The spectral shape differs too. Most white LEDs, in monitors, phones, and room lighting alike, work by driving a blue emitter in the 450-460 nm region through a phosphor that converts part of that output to longer wavelengths. The result is a characteristic spike near 450 nm rather than a smooth curve. That spike sits at the long end of the HEV range and near the circadian-sensitive band, which is why lens specifications tend to be quoted at 450 nm and across 460-480 nm. The practical implication is about timing rather than quantity. Evening exposure to the 460-480 nm region is the case where wavelength genuinely matters, and it is also the case where a heavily tinted lens is acceptable because you are not driving or color-matching.How to read a blue-light specification
A usable spec answers four questions. If any is missing, the number cannot be compared against anything.- Over what band? 400-500 nm, 380-500 nm, and a single point at 400 nm are three different measurements. A figure with no band is not a figure.
- Point value or average? 99.99% at 400 nm and 97.9% averaged across 400-500 nm describe very different curves.
- Weighted or unweighted? Hazard-weighted numbers apply a function peaking near 435 nm; unweighted averages treat every wavelength equally.
- Measured by whom, to what standard? Look for a named laboratory, an accreditation such as ISO/IEC 17025, and a test method such as ANSI Z80.3.