You might think the definition of a one act play would be easy (just count the acts), however sometimes playwrights create very short plays which they split into two or more acts.
In those cases, the playwright is thinking about the structure of the action.
However, for our definition of this category, we are talking about length.
We have opted for a very broad definition of the one-act category to include any play which might be expected to occupy half an evening's entertainment. (Generally, this is an item of up to seventy-five minutes duration, and usually it has very few changes of set.) Since we have set the lower cut-off limit of full-length plays at 60 minutes, there is a clear overlap!
We have set the lower limit of one-act plays at 20 minutes - anything below that fits into the Short play / 10-minute play / Sketch / Skit category.
One-Act Play Competitions
One-act play competitions usually have very specific boundaries for lenth. (From 20 minutes to 50 minutes is common.)
If you want something of a specific length, then use the Category search for One-Act Plays where you can set time boundaries to the nearest 5 minutes.
(Note that we use a calculated run time based on word count, assuming 1000 words on the page takes 6 minutes on the stage. Of course this varies enormously.)