The report abstract should contain important facets of the report.
It can include, purpose, key findings, significance and conclusion.
It is good to present all the information in most concise way so it is suggested to not go beyond the limit.
The abstract of lab report should be of one paragraph like 100 – 200 words.
It is because, such dissertations contain much information and making the summary of all the information requires some more words.
As abstract is a snapshot of complete paper, it should be concise and informative.It usually embraces reader to read the rest of the dissertation.So, not to take much time of reader; the abstract should be of 200 to 350 words in range.A good abstract is that which gives all the information of paper.It gives the idea to the reader whether he should read the complete paper or not.Also, it is suggested to not write the abstract in future tense.The range of abstract of journal articles is between 75 to 150 words.Every paper has its own requirements, where the scientific paper is concern; the abstract length of scientific papers is limited to 250 words maximum.So, it is better to write fewer words than the given limit.In Harvard styles, abstracts mostly ranges from 100 to 300 words in length.But it is better to ask from professor because some universities have their own requirement for the abstract.