Crop Factor Calculator – 35 mm Equivalents
Use sensor dimensions to compare focal length and depth of field with a nominal 36 × 24 mm frame.
Formula
c = √(36²+24²)/√(w²+h²); fₑ = fmc; Nₑ = Nmc (dimensions in mm).
Sensor width: 24 mm · Sensor height: 16 mm · Lens focal length: 50 mm · Crop factor ≈ sqrt(0.036^2+0.024^2)÷sqrt((24 mm × 0.001 m/mm)^2+(16 mm × 0.001 m/mm)^2) · Equivalent focal length ≈ (50 mm × 0.001 m/mm)×1000×(1)×(1.5) · Equivalent f-number (depth of field) ≈ (4)×(1)×(1.5)
How to use
- Enter the active sensor width and height.
- Enter focal length, f-number and adapter multiplier (1 without an adapter).
- Read crop factor and full-frame equivalents.
Examples
- A 24 × 16 mm sensor with a 50 mm f/4 lens gives 1.5×, 75 mm and f/6 equivalents.
Frequently asked questions
Does crop change the physical focal length?
No. Equivalent focal length describes field of view; an optical adapter can change actual focal length.
Is equivalent aperture an exposure setting?
No. It compares depth of field at matching framing and viewing conditions. Sensor crop alone does not change exposure f-number.
Which sensor size should I use?
Use the active image area, including any video crop. Different aspect ratios only match the diagonal field of view.
Sources
Updated: