Focal Length Equivalent Calculator

About the Focal Length Equivalent Calculator

The Focal Length Equivalent Calculator converts focal lengths between different camera sensor formats using crop factors. Enter any focal length and see the full-frame equivalent, the resulting field of view, and the depth-of-field-equivalent aperture across sensor sizes from medium format to smartphone. It is a practical shortcut for comparing lenses before you commit to a camera system or a new lens purchase.

Sensor size affects how much of the lens's image circle is captured. A smaller sensor uses only the center portion of the image, effectively "cropping" the view and making it appear more telephoto. A 50mm lens on an APS-C camera (1.5× crop) frames like a 75mm lens on full frame. Understanding this equivalence is crucial for choosing lenses and achieving specific compositions.

This calculator goes beyond simple multiplication. It calculates field of view in degrees, the aperture needed to match depth of field across formats, and provides a reference of common lenses with their equivalents on major sensor sizes.

When This Page Helps

Use this calculator when you want a crop-factor comparison before buying or mounting a lens on a different camera system. It is useful for choosing focal lengths, estimating framing, and matching depth of field across sensor sizes. That makes it easier to predict the look of a shot before you switch formats or rent a lens.

How to Use the Inputs

1. Enter the actual focal length of your lens.
2. Select the source sensor format.
3. View the equivalent focal length on every other format.
4. Check the field-of-view angle (horizontal and diagonal).
5. Compare aperture equivalents for matching depth of field.
6. Use the lens reference table for common configurations.

Example Calculation

Tips & Best Practices

• When shopping for lenses on APS-C, think in 35mm equivalents to judge framing.
• A 35mm lens on APS-C (52mm equiv) is a great general-purpose focal length.
• Ultra-wide angles are harder to achieve on crop sensors — 10mm on APS-C is only 15mm equiv.
• Teleconverters multiply focal length AND crop factor — a 200mm + 1.4× TC on APS-C = 420mm equiv.
• For matching shallow DOF on MFT, you need lenses 2 stops faster than full-frame lenses.

Understanding Sensor Sizes

The "full frame" standard (36×24mm) comes from 35mm motion picture film. It became the reference point for focal length equivalence. Anything smaller is "crop" and anything larger is "medium format."

APS-C (~23.5×15.6mm for Nikon/Sony, ~22.3×14.9mm for Canon) captures about 44% of the area of full frame. Micro Four Thirds (17.3×13mm) captures about 25%. A smartphone sensor (1/1.3" ≈ 9.6×7.2mm) captures only about 8% of a full-frame sensor area.

Practical Lens Equivalence

Instead of memorizing crop factors, learn the visual effect: On APS-C, a 35mm feels like a 50mm "standard" view. A 23mm feels like a 35mm "documentary" view. A 56mm feels like an 85mm "portrait" view. On MFT, a 25mm ≈ 50mm, 42.5mm ≈ 85mm, 12mm ≈ 24mm.

Trade-offs of Sensor Size

Larger sensors offer shallower DOF, better low-light performance, and higher resolution. Smaller sensors enable smaller/lighter bodies and lenses, greater effective reach for wildlife/sports, and deeper DOF (useful for landscapes). Neither is objectively "better" — it depends on your photographic priorities.

Frequently Asked Questions

• What is crop factor?

  Crop factor is the ratio of a full-frame sensor diagonal (43.3mm) to the diagonal of a smaller sensor. APS-C ≈ 1.5× (Nikon/Sony) or 1.6× (Canon). Micro Four Thirds = 2×. A 1-inch sensor ≈ 2.7×.

• Does crop factor change the actual focal length?

  No. A 50mm lens is always 50mm regardless of the sensor. Crop factor describes the change in field of view and effective framing compared to full frame. The lens's optical properties don't change.

• Why do phone cameras claim "24mm equivalent"?

  Phone sensors are tiny (crop factor 5-8×), so a 5mm lens provides the same field of view as a 24mm lens on full frame. The "equivalent" label helps users compare framing to traditional cameras.

• Does crop factor affect depth of field?

  Indirectly, yes. A smaller sensor at the same framing uses a shorter actual focal length, producing deeper DOF. To match full-frame DOF, multiply the aperture by the crop factor: f/2.8 on APS-C ≈ f/4.2 DOF on full frame.

• Is medium format better because of less crop?

  Medium format sensors are larger than "full frame" (which is really just 35mm film frame). They have crop factors less than 1 (0.79× for Fuji GFX). This gives shallower DOF and wider FOV at the same focal length.

• What is the "normal" focal length for each format?

  The "normal" lens roughly equals the sensor diagonal. Full frame: ~43mm (practically 50mm). APS-C: ~28mm (practically 35mm). MFT: ~22mm (practically 25mm). Medium format: ~55mm (practically 80mm).