Interpupillary distance

Interpupillary distance (IPD) is the distance between the pupils of your eyes. There are two types of IPDs: Real IPD and Virtual IPD.

A bar chart of average IPD in humans

Most adult humans have an IPD of about 63mm.

IPD can be measured in a number of ways.

Some VR headsets have an IPD adjustment. The Oculus Rift DK1, DK2, and HTC Vive have manual IPD adjustment. And the Valve index too.

Mirror measurement

IPD can be measured using a mirror.

It can be measured by standing close to a vertical mirror, and close one eye at a time. Each eye look directly into that eye on the mirror, use a marker to mark a spot on the mirror where the pupil is. The distance between the dots is a measurement of IPD.

Real IPD

Real IPD is the actual distance between the center of your eyes' pupils in real life. Any Head-mounted Display require this measurement to accurately position the virtual camera outputs on the screen in front of the user's eyes. The outputs have to be directly in front of both of the users' eyes. Any deviation can cause eye strain. Most HMDs allow users to adjust their camera output positions to match their IPD.

Additionally, some HMDs allow the physical position of the lenses and screens to be adjusted to match the user's physical IPD.

The average IPD for humans is 64 millimeter, with a range of 54 to 72 millimeter. You can measure your IPD by measuring the distance between the center of your pupils with a ruler.

Virtual IPD

Virtual IPD, sometimes referred to as ICD (Inter Camera Distance) or VCS (Virtual Camera Separation), is the distance between the 2 virtual eyes (cameras) in Virtual Reality. This number can change the Sense of Scale of the objects in the virtual environment in relation to the user.

Developers can change the sense of scale by changing virtual IPD. They can cause the environment to increase or decrease in size by changing the virtual IPD.