Depth of field (DOF) is the range of distances in a photo that appear acceptably sharp. It depends on four things: the lens focal length, the aperture, how far away you focus, and the sensor format — which sets the "circle of confusion," the largest blur spot still perceived as a point. This calculator computes the near and far limits of sharpness, the total depth of field, and the hyperfocal distance: the focus distance at which everything from half that distance to infinity is sharp. Wider apertures (smaller f-numbers), longer lenses, and closer subjects all shrink the depth of field; stopping down, using a shorter lens, or focusing farther away expands it. When your focus distance reaches or exceeds the hyperfocal distance, the far limit extends to infinity.

How it works — the formula

Hyperfocal  H = f²/(N·c) + f
Near limit   = H·s / (H + (s − f))
Far limit    = H·s / (H − (s − f))   [∞ if s ≥ H]
(f, c in mm; s = focus distance)

The hyperfocal distance sets the scale of sharpness for a given focal length, aperture, and circle of confusion. Near and far limits are derived from it and the focus distance; the far limit diverges to infinity once you focus at or beyond the hyperfocal distance.

Source: Wikipedia — Depth of field (formulae & CoC)

Worked examples

Example 1

50 mm, f/8, 3 m, full frame

Inputs:: focal=50, aperture=8, distance=3, sensor=ff
Output:: H≈10.8 m, near 2.36 m, far 4.12 m, DOF≈1.77 m

Example 2

24 mm, f/11, 2 m, full frame

Inputs:: focal=24, aperture=11, distance=2, sensor=ff
Output:: H≈1.83 m; 2 m ≥ H → far = ∞

Example 3

85 mm, f/1.8, 1.5 m, full frame

Inputs:: focal=85, aperture=1.8, distance=1.5, sensor=ff
Output:: DOF ≈ 0.03 m (very shallow)

Limitations

Circle of confusion is a convention (sensor diagonal ÷ 1500); your sharpness standard may differ.
Diffraction softening at small apertures is not modelled.
Assumes the focus distance is measured to the subject, not the sensor plane offset.

DOF is perceptual; treat the limits as guidance, not a hard sharp/blurred boundary.

Frequently asked

What is depth of field?+

Depth of field is the zone, from a near limit to a far limit, in which objects look acceptably sharp in the final image. Outside that zone, detail blurs progressively. It is a perceptual range, defined relative to a circle of confusion that depends on sensor size and viewing conditions.

What is the hyperfocal distance?+

The hyperfocal distance is the closest focus distance at which the far limit of depth of field reaches infinity. Focusing there maximises DOF: everything from half the hyperfocal distance out to infinity is acceptably sharp. It is widely used in landscape photography.

What is the circle of confusion?+

It is the largest blur spot on the sensor that still looks like a sharp point in the final print or screen view. Smaller sensors use a smaller circle of confusion (roughly the sensor diagonal ÷ 1500), which is why this calculator asks for your format — full frame uses about 0.029 mm, APS-C about 0.019 mm.

How does aperture affect depth of field?+

A smaller aperture (larger f-number, e.g. f/16) increases depth of field; a wider aperture (smaller f-number, e.g. f/1.8) shrinks it for a blurred background. Each stop down roughly proportionally extends the hyperfocal-based limits, though diffraction softens the whole image at very small apertures.

Why is depth of field not symmetric around the subject?+

For typical distances, more of the in-focus zone falls behind the subject than in front — often roughly one-third in front and two-thirds behind, though the exact split varies with distance. This calculator shows the front and rear portions separately.

Does a crop sensor change depth of field?+

Yes. For the same framing and aperture, a smaller sensor has greater depth of field because it uses a shorter actual focal length and a smaller circle of confusion. Selecting the correct format here accounts for the circle-of-confusion part of that effect.