How does the capacity of a Blu Ray DVD compare with that of a standard DVD?

Single-layered DVDs hold around 4.7gigabytes, with Dual-layered DVDs holding around 8.5gb A single layered Blu-Ray disc can hold up to 25gb, with a dual-layer holding up to 50gb. There is also a Holographic Versatile Disc (HVD) in the research stage that, if it works, will be able to hold up to 3.9 terabytes.