One form of DVD discs that means a single-sided dual-layer DVD disc. DVD-9 can hold approximately 7.95 gigabytes of data, even though marketers like to use the 8.5GB value instead, but this is misleading and is calculated by using so-called "Japanese gigabytes" which means that gigabyte is calculated as 1,000 megabytes, but in real computer terminology, gigabyte is 1,024 megabytes.
DVD-9 DVD-Video discs are problematic for DVD-R owners, because the cheap, writable single-layer DVDR discs can only hold the same amount of data that DVD-5 discs contain, due technical reasons. However, there are several ways to copy a DVD-9 disc to a standard, single layer DVD-R or DVD+R disc -- we have several guides available how to do this on our guide section.
DVD-9 is nowadays often used as the marketing term for dual layer DVD-R and DVD+R discs and use of that name is quite appropriate as the dual layer recordable discs can hold exactly the same amount of data as "pressed" DVD-9 discs can.
Other regular DVD size acronym: