Sunglasses Size Calculator

Optometry & Eyewear Frame Anatomy

Every pair of prescription glasses and quality sunglasses has three standardized measurements printed on the inside of the left temple arm: [Lens Width] □ [Bridge Width] [Temple Length] (e.g. 54 □ 18 145).

Primary Optical Frame Parameters

• Lens Width (Eye Size, A): The horizontal diameter of one lens at its widest point (48 to 62 mm).

• Bridge Width (DBL): The shortest distance between the two lenses across the nose bridge (14 to 24 mm).

• Temple Arm Length: The full length of the side arm from hinge to curved ear tip (135 to 150 mm).

• Total Frame Front Width:

Frame Front = (2 × Lens Width) + Bridge Width + Endpieces (approx 6 mm)

The Standard Credit Card Test

Standard credit cards have an international standardized width of 85.6 mm. Stand in front of a mirror, place one vertical edge of the card at the center of your nose bridge:

• Card extends beyond the corner of your eye: Small / Narrow Fit (< 50 mm lens).

• Card touches the outer corner of your eye: Standard / Medium Fit (52 - 55 mm lens).

• Card ends before the outer corner of your eye: Large / Wide Fit (56 - 62 mm lens).

How to Use This Calculator

Enter your Temple-to-Temple Face Width (mm) (e.g. 135 in mm), Face Shape — choose from Oval (Balanced — Fits almost all frame styles), Round (Full cheeks — Rectangular & angular frames), Square (Strong jawline — Round & Aviator frames), and Desired Sunglasses Style — choose from Classic Wayfarer / Acetate Square, Teardrop Aviator / Metal Wire, Browline / Clubmaster Hybrid. Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Formula Reference: Sunglasses Size Calculator

Input variables:

templeToTempleFaceWidthMm — Temple-to-Temple Face Width (mm)

faceShapeSelect — Face Shape

sunglassesStyleSelect — Desired Sunglasses Style

Computed outputs:

recommendedFitCategory — Recommended Frame Fit Category

recommendedLensWidthRange — Recommended Lens Width

recommendedBridgeWidthRange — Recommended Bridge Width

recommendedTempleLengthRange — Recommended Temple Arm Length

totalFrameFrontWidthMm — Total Frame Front Width

Mathematical relationships extracted from calculation logic:

frameFront = Math.round(faceMm * 0.98)

Standard: NIST / ISO mathematical definitions

Worked Example

A person with a 135 mm face width measuring across their cheekbones fits a standard 52-18-145 frame perfectly, providing optimal ocular coverage without temple pinching.

Understanding Your Result

Evaluate your result in the context of your specific use case and relevant industry standards or reference values. A single calculated result is a starting point — test two to three scenarios to understand how sensitive the outcome is to your key input assumptions. For high-stakes decisions, verify your result against a secondary source or subject-matter expert before acting.