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 and light): 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 APS-C looks like an 80mm on full frame
• Equivalent Aperture — the f-number that produces equivalent background blur and light sensitivity; f/2.8 on APS-C ≈ f/4.2 on full frame for depth of field

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 while the lens is fast at f/1.4 physically, the depth of field is shallower than a true 35mm f/1.4 full-frame lens — but still noticeably shallower than f/2 on full frame.

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 — valuable for wildlife and sports.