okay so if you're writing a 10,000 word dissertation right now and you've found yourself typing how long should a literature review be in a 10000 word dissertation into google then firstly welcome because you are in very good company and secondly i promise this thread is going to give you the clear straightforward answer that you actually came here for rather than the vague unhelpful non answers that seem to make up about 90 percent of the advice available online i've been through this exact process myself and i know how much of a difference it makes to just have someone tell you plainly what you need to know so here we go.
for a 10,000 word dissertation your literature review should sit at roughly 2,000 to 3,000 words and that figure comes from the widely accepted 20 to 30 percent of total word count rule that the vast majority of UK universities apply at undergraduate level.