How to Write a Lab Report

You’ve finished the experiment. Your lab bench is a mess, your notebook is full of cryptic data, and now you have to write the lab report. For many students, this is the hardest part.

A lab report is not a creative essay; it is a rigid, formal document. Its goal is to clearly and objectively communicate *what* you did, *why* you did it, *what* you found, and *what it means*.

This guide is your foundational resource for lab reports and scientific writing. We will cover the “micro” skills for each section, from the Abstract to the Conclusion, so you can write a clear, professional, and high-scoring report.

What is a Lab Report?

A lab report is a formal document that describes and analyzes a scientific experiment. It follows a specific, logical structure known as the IMRaD format. This format allows other scientists to understand and, most importantly, *reproduce* your experiment.

Purpose of a Lab Report

A lab report is the backbone of the scientific method. Its purpose is to:

• Document: Create a formal record of your hypothesis, methods, and results.
• Communicate: Clearly explain your findings to your professor or peers.
• Analyze: Interpret your data and explain what it means in the context of your hypothesis and existing scientific knowledge.

Lab Report vs. Research Paper

These two are similar but have one key difference:

Think of a lab report as your training for writing a full research paper.

The Core Components (IMRaD Structure)

Nearly all scientific reports follow the IMRaD format: Introduction, Methods, Results, and Discussion. As the UNC Writing Center notes, this structure is the “standard for scientific writing.” Your report must include these sections, plus a few others.

1. Title Page

A specific, descriptive title. Not “Chemistry Lab,” but “The Effect of Temperature on the Rate of Enzyme Catalysis in *H. Pylori*.” Also include your name, course number, and lab partners’ names.

2. Abstract

The abstract is a 150-250 word summary of the *entire* report. Write it last. It must include:

• Purpose: The objective of the experiment.
• Methods: A brief 1-2 sentence overview of what you did.
• Key Results: The most important finding (e.g., “The rate of reaction doubled.”).
• Conclusion: The main takeaway from your experiment.

3. Introduction

This section answers “Why did you do this?” It provides the background for your experiment.

• Background: What scientific knowledge already exists on this topic?
• Purpose: State the specific objective of *your* experiment.
• Hypothesis: State your testable prediction (e.g., “If the temperature increases, then the reaction rate will increase.”).

4. Materials and Methods

This section answers “What did you do?” It must be so detailed that someone else could repeat your experiment.

• Materials: A list of all equipment and chemicals used.
• Procedure: A step-by-step description of your experiment.
• Important: Write this in the past tense and third-person.
  • Incorrect: “First, I will pour 20mL of acid”
  • Correct: “Twenty (20) mL of 1M HCl was poured into a 50mL beaker.”

5. Results

This section answers “What did you find?” This is where you present your raw data, objectively. Do not interpret the data here.

• Data Tables: The most common way to show raw data. Must have clear, numbered titles (e.g., “Table 1. Change in Temperature over Time”).
• Graphs/Figures: Visual representations of your data (e.g., line graphs, bar charts). Must have numbered, descriptive titles (e.g., “Figure 1. Reaction Rate vs. Substrate Concentration”).
• Text: A brief paragraph that walks the reader through your tables and figures, pointing out the key findings (e.g., “As shown in Figure 1, the reaction rate…”).

6. Discussion

This is the most important section. It answers “What does it mean?” This is where you interpret your results.

• Analysis: What do your results mean? How do they relate to your hypothesis?
• Hypothesis: State whether your hypothesis was supported or rejected by the data.
• Error Analysis: What went wrong? What errors (human or systematic) could have affected your data?
• Future Work: How could this experiment be improved? What is the next step?

7. Conclusion

A brief 1-2 paragraph summary of your findings. It should restate your hypothesis, your main result, and the primary conclusion from your discussion. See our guide on how to write a conclusion for more.

8. References (Citations)

List all sources you cited (e.g., your lab manual, background articles). Common styles include APA, ACS (American Chemical Society), or CSE (Council of Science Editors).

How to Write a Lab Report (7-Step Process)

Writing a lab report is not a linear process. Use this strategic order.

You cannot write about an experiment you don’t understand. Review your lab manual and notes. What was the *point*? What was your testable hypothesis?

Write the “easiest” sections first, while the experiment is fresh. The Methods (what you did) and Results (what you found) are objective facts. Organize your data into tables and graphs.

This is the “thinking” part. Look at your results. What trends do you see? Was your hypothesis supported? Why or why not? Write the Discussion section next, as it’s the most critical part.

Now that you know what you found (Results) and what it means (Discussion), you can write the Introduction. You can now properly set the stage and lead the reader to your hypothesis.

Summarize the key findings from your Introduction, Results, and Discussion into a final, brief concluding paragraph.

Now that you have all other sections complete, write the 1-paragraph summary of the entire paper. This is the last thing you write.

Create your specific title, format your References section, and proofread the entire document for clarity, objectivity, and errors.

Tips for Specific Sciences

• Chemistry Lab Report: Focus heavily on chemical reactions, stoichiometry, and error analysis. Data is often presented in detailed tables. The ACS citation style is common.
• Biology Lab Report: Focus on the hypothesis, organism behavior, and biological processes. Often includes observational data. APA style is common.
• Physics Lab Report: Focus on theoretical principles, equations, and a deep analysis of calculated vs. theoretical values (percent error). Graphs are critical.

Formatting Data: Tables vs. Graphs

A common question is when to use a table vs. a graph. As this article on data presentation explains, the choice depends on your goal.

• Use a Table: When you need to show many precise, individual data points (e.g., 20 different measurements).
• Use a Graph (Figure): When you want to show a *trend* or *relationship* between variables (e.g., a line graph showing change over time).

All tables and figures must be numbered and have a clear, descriptive title *above* the table or *below* the figure (depending on citation style).

Common Pitfalls

Avoid these common mistakes to improve your grade.

As this guide for writing scientific papers advises, “The main goal is clarity… a scientific paper is a *story*… about a question and the quest to answer it.”