Getting your timing right is one of the biggest challenges for inexperienced speakers. The following tips will help you with this:

• A good presentation speaking speed is about 100 words per minute.
• How long it takes to get through any particular slide depends on what’s on it, but as a rule of thumb there should be fewer slides than there are minutes for your presentation, and the longer your talk, the bigger the difference between minutes and number of slides there needs to be.
• Mental rehearsals go much faster than do live presentations, so don’t judge how long your talk will take by how long it takes you to go through it in your head. To get a better idea, give a performance out aloud.

Another aspect of timing is pacing your presentation. While it’s important to give an enthusiastic presentation, it’s also important that you have brief pauses after important or complicated points in order to emphasise them or to give the audience a chance to take them in. (Pay careful attention to how academics who are really effective presenters do this.)