I analyzed a random sample of 61,519 full-text research papers, uploaded to PubMed Central between the years 2016 and 2021, in order to answer the questions:
What is the typical overall length of a research paper? and how long should each section be?
I used the BioC API to download the data (see the References section below).
Here’s a summary of the key findings
1- The median length of a research paper is 4,133 words (equivalent to 166 sentences or 34 paragraphs), excluding the abstract and references, with 90% of papers being between 2,023 and 8,284 words.
2- A typical article is divided in the following way:
- Introduction section: 14.6% of the total word count.
- Methods section: 29.7% of the total word count.
- Results section: 26.2% of the total word count.
- Discussion section: 29.4% of the total word count.
Notice that the Materials and methods is the longest section of a professionally written article. So always write this section in enough depth to provide the readers with the necessary details that allow them to replicate your study if they wanted to without requiring further information.
Overall length of a research paper
Let’s start by looking at the maximum word count allowed in some of the well-known journals. Note that the numbers reported in this table include the Abstract, Figure legends and References unless otherwise specified:
|Journal||Maximum Length Allowed|
for Original Research Papers
|Maximum Length Allowed|
for Review Papers
|Nature||9,000 words ||9,000 words |
|Elsevier Journals||8,000 words||8,000 words|
|Cancer||5,000 words||6,000 words|
|Neurology||4,850 words [1,2]||5,350 words [1,2]|
|Science||4,500 words||6,000 words|
|Blood||4,000 words [1,2]||4,000 words [1,2]|
|Annals of Internal Medicine||3,775 words ||4,275 words |
|Journal of Clinical Psychiatry||3,250 words [1,2]||5,250 words [1,2]|
|Pediatrics||3,000 words||4,000 words|
 excluding figure legends
 excluding references
A review paper is either a systematic review or a meta-analysis, and an original research paper refers to either an observational or an experimental study conducted by the authors themselves.
Notice the large variability between these journals: The maximum number of words allowed ranges between 3,000 and 9,000 words.
Next, let’s look at our data.
Here’s a table that describes the length of a research paper in our sample:
|Minimum||271 words||12 sentences||4 paragraphs|
|25th Percentile||3,118 words||125 sentences||26 paragraphs|
|50th Percentile (Median)||4,113 words||166 sentences||34 paragraphs|
|Mean||4,539 words||184 sentences||40 paragraphs|
|75th Percentile||5,494 words||220 sentences||46 paragraphs|
|Maximum||48,163 words||3,438 sentences||1,736 paragraphs|
90% of research papers have a word count between 2,023 and 8,284. So it will be a little weird to see a word count outside of this range.
Our data also agree that a typical review paper is a little bit longer than a typical original research paper but not by much (3,858 vs 3,708 words).
Length of each section in a research article
The median article with an IMRaD structure (i.e. contains the following sections: Introduction, Methods, Results and Discussion) is in general characterized by a short 553 words introduction. And the methods, results and discussion sections are about twice the size of the introduction:
|Median Word Count||Length in Percent|
of the Total Word Count
|Introduction Section||553 words||14.6%|
|Methods Section||1,126 words||29.7%|
|Results Section||991 words||26.2%|
|Discussion Section||1,115 words||29.5%|
For more information, see:
- How Long Should a Research Title Be? Data from 104,161 Examples
- How Long Should the Abstract Be? Data 61,429 from Examples
- How Long Should the Introduction of a Research Paper Be? Data from 61,518 Examples
- How Long Should the Methods Section Be? Data from 61,514 Examples
- How Long Should the Results Section Be? Data from 61,458 Examples
- How Long Should the Discussion Section Be? Data from 61,517 Examples
- Length of a Conclusion Section: Analysis of 47,810 Examples
- Comeau DC, Wei CH, Islamaj Doğan R, and Lu Z. PMC text mining subset in BioC: about 3 million full text articles and growing, Bioinformatics, btz070, 2019.