Sensor Crop Factor Calculator

Crop factor describes the size ratio between a camera sensor and the 35mm full-frame standard (36mm × 24mm). It determines how a lens’s field of view is affected when used on a crop sensor camera. Understanding crop factor is essential when comparing lenses, building a kit, or switching between camera systems.

Crop Factor formula: Crop Factor = Full-Frame Diagonal / Sensor Diagonal

Full-Frame Diagonal = √(36² + 24²) = √(1296 + 576) = √1872 = 43.27 mm

Equivalent Focal Length: Equivalent FL = Actual Focal Length × Crop Factor

Equivalent Aperture (for depth of field only, never for exposure): Equivalent f-number = Actual f-number × Crop Factor

What each variable means:

• Crop Factor, the multiplier that converts an actual focal length to its full-frame equivalent field of view; APS-C Canon = 1.6×, APS-C Nikon/Sony/Fuji = 1.5×, Micro Four Thirds = 2.0×, 1" sensor = 2.7×
• Equivalent Focal Length, the full-frame focal length that produces the same angle of view; a 50mm on Canon APS-C looks like an 80mm on full frame
• Equivalent Aperture, the f-number that produces equivalent background blur at matched framing; f/2.8 on APS-C gives the same depth of field as f/4.2 on full frame. It does not convert exposure. An f/2.8 lens meters as f/2.8 on every camera ever made, and your shutter speed does not change when you switch bodies.

Worked example: Fujifilm X-T5 (APS-C, crop factor 1.5×). Lens: 23mm f/1.4.

Equivalent FL = 23 × 1.5 = 34.5mm (close to the classic 35mm “street photography” look on full frame) Equivalent aperture = f/1.4 × 1.5 = f/2.1 (for depth of field comparison)

So the lens meters as a genuine f/1.4 and you get f/1.4 shutter speeds. What you do not get is f/1.4 background blur at full-frame framing: the blur matches a 34.5mm f/2.1 lens on full frame, which is a stop less separation than a true 35mm f/1.4 would give you. Still shallow, just not as shallow as the number on the barrel suggests.

Common sensor crop factors: Full Frame (35mm): 1.0× | APS-C (Canon): 1.6× | APS-C (others): 1.5× | Micro Four Thirds: 2.0× | 1-inch: 2.7× | 1/2.3" (compact): 5.6×

When crop factor helps: APS-C and MFT sensors give telephoto reach at lower weight and cost. A 300mm f/5.6 on APS-C equals 450mm full-frame reach, which is valuable for wildlife and sports.