NHGRI logo

Kilobase (kb)

updated: June 23, 2024


A kilobase (abbreviated kb) is a unit of measurement used to help designate the length of DNA or RNA. One kilobase is equal to 1,000 bases.



Kilobase. It can be useful to think of a kilobase in the similar way we think of computer kilobytes. We hear of kilobytes when we describe computer memory. It simply refers to how much information a memory chip can store. When I was growing up memory chips and computers were measured in hundreds of kilobytes. Well, that's not a lot by today's standards. And that is a useful analogy, because in biology we tend to use kilobases when we describe the size of single gene or DNA. In contrast, when we describe genomes, the collection of all genes in an organism and its non coding DNA, we need to use a much larger unit, such as gigabase. In a similar way, we started using gigabytes to describe much larger memory chips and modern computers.

Oleg Shchelochkov
Oleg A. Shchelochkov, M.D.


Medical Genetics and Genomic Medicine Training Program