Understanding the ISO 8624 Standard for Eyeglass Frame Measurements
A unified international system that ensures consistency and precision in eyewear sizing, labeling, and manufacturing.
What is ISO 8624?
ISO 8624, officially titled “Spectacle frames — Measuring system and terminology”, is an international standard established by the International Organization for Standardization (ISO). The latest version, ISO 8624:2020, defines how spectacle frames should be measured and described, creating a universal language for optical manufacturers, suppliers, and retailers.
It specifies the key dimensional terms for the frame front, lens boxing system, and temples, ensuring that frame sizes are comparable and consistent across countries and production systems.
Key Measurement Terms in ISO 8624
| Term (Symbol) | Description |
|---|---|
| A (Horizontal boxed lens size) | The width of the lens box, measured from the left to right vertical tangent lines. |
| B (Vertical boxed lens size) | The height of the lens box, measured from the upper to lower horizontal tangent lines. |
| DBL or d (Distance between lenses) | The shortest horizontal distance between the two boxed lenses at the bridge area — commonly known as the bridge size. |
| TL or l (Overall temple length) | The total length of the side piece, from the hinge axis to the end tip. |
Note: The standard also defines additional geometric terms such as “face-form angle,” “boxed center,” and “distance between boxed centers,” which are used in frame design and optical fitting processes.
Why ISO 8624 Matters to the Optical Industry
- ✅ Consistency: Ensures all manufacturers use the same dimensional references worldwide.
- ✅ Quality Control: Standardized measurements reduce production errors and improve fitting precision.
- ✅ Professional Labeling: Builds consumer trust through clear and accurate size marking (e.g. 52–18–140).
- ✅ Better Communication: Facilitates smooth specification exchange between designers, OEM factories, and distributors.
- ✅ E-commerce Compatibility: Enables reliable online comparison and frame recommendation systems.
Important Notes & Limitations
ISO 8624 defines how to measure eyeglass frames, but it does not define what counts as a small, medium, or large frame. The classification of “size” remains subjective and depends on regional fit preferences, gender, and facial geometry.
- Manufacturers can apply their own fit categories (e.g. Asian Fit, European Fit, Petite, Oversized) using ISO 8624 dimensions as a foundation.
- Retailers and e-commerce platforms often combine ISO 8624 data with consumer facial width or AI try-on systems for accurate sizing recommendations.
Source: ISO 8624:2020 — Spectacle frames: Measuring system and terminology, International Organization for Standardization.
When your eyewear follows ISO 8624 standards, your measurements speak a global language.
Whether you are a designer, manufacturer, or distributor, adopting this standard enhances precision, communication, and brand professionalism.