In case of a DVD, the speed of data transfer is mentioned in multiples of?

Optical-disc drive speeds (CD, DVD, Blu-ray) are always expressed as multiples of a fixed 1x base transfer rate, a constant defined by each medium's own standard. Because each medium's track pitch and rotational specification differ, CD and DVD use different 1x constants — quoting one medium's base rate for another produces a wrong answer.

1. For DVD, the base (1x) transfer rate is standardized (ECMA-267 / ISO-IEC 16448) at 11.08 Mbit/s.

2. Converting to bytes: 11.08 Mbit/s ÷ 8 = 1.385 MB/s, which rounds to the commonly quoted 1.38 MB/s.

3. A drive's rated speed is then this base rate multiplied by its speed factor — e.g. a 16x DVD drive transfers at roughly 16 × 1.38 MB/s ≈ 22.1 MB/s.

This distinguishes the DVD base rate from the CD-ROM base rate of 150 KB/s (roughly 9x smaller) — the two media are never described using the same 1x constant, which is why manufacturer spec sheets always state whether a rating is 'x' for CD or for DVD.