How Much Space Is on a DVD Disc?

A DVD records its information in a long spiral, extending outward from the center of the disc. The spiral contains little divots in it--each exactly the same width and depth--which combine to form a binary code. That code carries the audio and video information of the movie on the DVD, which your player then translates and places onscreen.

Lasers

The size of a DVD is determined by the length of the spiral. The coding in the spiral is read by a laser, which is accurate enough to distinguish individual lines in the grooves.

Layers

Information in a DVD may be divided into multiple layers and/or have data encoded on both sides, which can increase the storage capacity of the disc.

Hiccups

Have you ever noticed a slight pause in the action when you watch a DVD? That's caused by the layers switching layers to continue reading the information.

Size

A single-layer DVD can hold about 4.7 gigabytes worth of information. Double layers can hold a little less than twice that amount: 8.5 gigabytes.

Length

A single layer of the average DVD (4.7 Gb) translates into about 2 hours worth of movie time. Double-layered DVDs can hold about 4 hours worth.