How to Write a Lab Report: Step-by-Step Guide for University

The IMRAD format, section by section. What your TA actually wants to see - and what loses marks.

1. Lab Report Structure (IMRAD)

Almost every university lab report follows the IMRAD format: Introduction, Methods, Results, Analysis, and Discussion. Some courses merge Analysis into Discussion, and some add a separate Conclusion. But the skeleton is always the same.

Here is what each section does at a glance:

• Introduction - Why you did the experiment. Background, hypothesis, purpose.
• Methods - What you did. Procedure, materials, setup.
• Results - What you found. Data, tables, figures. No interpretation.
• Analysis / Discussion - What it means. Interpret data, explain errors, connect to theory.

The logic flows like a story: you set up the question, describe how you tested it, show what happened, and explain what it all means. Every section answers a different question, and your TA is grading each one separately. Mixing them up - like interpreting data in your Results section - is one of the fastest ways to lose marks.

2. Title Page

The title page is the simplest part of your report, but getting it wrong looks careless. Most courses want a standalone page with the following information:

• Title of the experiment - Specific and descriptive, not just "Lab 4." A good title names the variables: "The Effect of Temperature on Enzyme Activity" tells the reader exactly what the report covers.
• Your full name and student number
• Course code and section - e.g., CHEM 1A03, Section L07
• TA name - yes, this matters
• Lab partner(s) - list full names
• Date of the experiment - the day you performed it, not the day you wrote the report
• Date submitted

Some departments have a specific title page template. If one exists, use it exactly. If not, center everything vertically on the page, use a clean font, and move on. Do not spend 45 minutes making it look fancy.

3. Abstract

Not every lab report requires an abstract - check your course guidelines. When it is required, the abstract is a standalone summary of the entire report in 150-250 words. A reader should be able to understand your experiment, results, and conclusion without reading anything else.

What to Include

1. Purpose - One sentence on what was investigated and why
2. Methods - Brief description of procedure (1-2 sentences)
3. Key results - The most important numerical findings
4. Conclusion - Whether the hypothesis was supported

How to Write It

Write the abstract last, after you have finished every other section. You are summarizing work that is already done - trying to write it first means guessing at your own results. Use past tense throughout. Do not include citations, figures, or information that is not in the report itself.

4. Introduction

The introduction tells the reader why this experiment exists. It is not a recap of the lab manual - it is your job to provide context, state what you expected, and explain why anyone should care.

Structure Your Introduction Like a Funnel

1. Broad context - What is the scientific concept being explored? (1-2 sentences)
2. Narrowing - What specific aspect does this experiment address? Why is it important? (2-3 sentences)
3. Relevant theory - What equations, laws, or principles apply? Define key terms. Cite sources.
4. Hypothesis - What did you predict and why? Be specific and testable.
5. Purpose statement - One clear sentence: "The purpose of this experiment was to..."

Common Introduction Mistakes

• Copying from the lab manual - Your introduction should be in your own words. TAs know the manual.
• No hypothesis - A hypothesis is a prediction based on theory, not a guess. "We hypothesize that increasing temperature will increase reaction rate because higher kinetic energy increases molecular collisions (Arrhenius, 1889)."
• Too long - The introduction should be 1-2 pages, not five. Save the detail for Methods and Discussion.

5. Materials and Methods

The Methods section describes what you did in enough detail that another scientist could reproduce your experiment. That is the standard: reproducibility.

Key Rules

• Past tense - You already did the experiment. "The solution was heated," not "Heat the solution."
• Passive voice (usually) - "Absorbance was measured at 420 nm" is standard. Some courses now accept active voice ("We measured absorbance at 420 nm") - check with your TA.
• Narrative form, not a list - Do not write a recipe with bullet points. Write connected paragraphs that describe the procedure logically.
• Include specifics - concentrations, volumes, temperatures, equipment models, durations, number of trials
• Do not explain why - Save the reasoning for the Discussion. Methods is purely what was done, not why.

What NOT to Include

• Do not list equipment like a grocery list. Mention apparatus as it appears in the procedure.
• Do not include results or observations. If the solution turned blue, that goes in Results.
• Do not copy the lab manual. Your methods should describe what you actually did, including any deviations from the protocol.

If your procedure deviated from the lab manual (it almost always does - a measurement you had to repeat, a reagent you substituted), document that deviation. TAs want to know what actually happened, not the idealized version.

6. Results

Results is the most straightforward section: present your data clearly and let it speak for itself. No interpretation, no explanation, no opinion. Just what happened.

Presenting Data

• Tables for raw numerical data (measurements, calculated values). Every table needs a title above it (Table 1: Effect of Temperature on Reaction Rate) and clear column headers with units.
• Figures (graphs, images) for showing trends and relationships. Every figure needs a caption below it (Figure 1. Absorbance vs. concentration...) and axis labels with units.
• Text to walk the reader through key observations: "As shown in Table 1, the reaction rate increased from 0.12 to 0.38 abs/min as substrate concentration increased from 0.5 to 4.0 mM."

Describe Trends, Not Interpretations

There is a critical difference between describing and interpreting:

Formatting Rules

• Number all tables and figures sequentially (Table 1, Table 2... Figure 1, Figure 2...)
• Reference every table and figure in the text - if you do not mention it, delete it
• Use appropriate significant figures (match the precision of your instruments)
• Include units everywhere - values without units are meaningless
• Include error bars or standard deviations if you ran multiple trials

7. Discussion

This is where your grade is made or lost. The Discussion is the most heavily weighted section in almost every lab report rubric. It is where you show that you actually understand the science, not just followed instructions.

What to Cover

1. Interpret your results - What do the numbers mean? Do they support or refute your hypothesis? Be explicit: "The data support/do not support the hypothesis that..."
2. Connect to theory - Explain your results using the scientific principles from your Introduction. If your enzyme kinetics followed Michaelis-Menten, say so and explain what the K_m and V_max values tell you biologically.
3. Compare to literature - How do your values compare to published data? If your measured boiling point was 78.2°C and the literature value is 78.4°C, calculate the percent error and discuss the agreement.
4. Explain unexpected results - This is critical. If your results did not match expectations, do not pretend they did. Analyze why. Equipment limitations? Systematic errors? Incorrect assumptions? TAs reward honest analysis far more than fabricated agreement.
5. Discuss error and limitations - Identify specific sources of error (not "human error" - that means nothing). Be specific: "Parallax error in reading the meniscus" or "evaporative losses during prolonged heating" or "the spectrophotometer was calibrated only once during the 3-hour session."

Error Analysis Done Right

"Human error" is not a real source of error. Neither is "we might have measured wrong." Actual error analysis identifies specific, mechanistic sources:

• Systematic errors - Consistent bias in one direction (uncalibrated instrument, impure reagent, heat loss to environment). These shift all your data the same way.
• Random errors - Unpredictable variation (reading a graduated cylinder, timing a reaction by hand). These scatter your data around the true value.
• Procedural limitations - Only testing 5 concentrations instead of 20, or using a 10 mL graduated cylinder when a 1 mL micropipette would be more precise.

8. Conclusion

The Conclusion is short - 2-3 sentences, maybe a brief paragraph. Some courses fold it into the Discussion. When it is a separate section, it should do three things:

1. Restate the purpose - One sentence reminding the reader what you investigated.
2. Summarize key findings - Your most important result(s) with numerical values.
3. Connect to hypothesis - Was the hypothesis supported? Say so clearly and concisely.

Do not introduce new information in the Conclusion. Do not discuss error here (that belongs in Discussion). Do not write "In conclusion" - the section heading already says it.

9. References

Every source you cited in the report must appear in the References section, and every item in your References must be cited somewhere in the report. This is not a bibliography of everything you read - it is a specific list of works you referenced.

Common Formats in Science

APA (7th edition) - used in biology, psychology, health sciences:

CSE (Council of Science Editors) - used in chemistry, physics, engineering:

Your course will specify which format to use. If it does not, ask your TA. Consistency is more important than the specific style - pick one and apply it everywhere. Do not mix APA in-text citations with CSE reference list formatting.

What to Cite

• Textbook - for theory and equations
• Lab manual - for the procedure (if your course requires it)
• Published literature values - for comparison in your Discussion
• Any external sources you used for background information

10. Common Mistakes That Lose Marks

After grading hundreds of lab reports, TAs see the same mistakes every semester. Avoid these and you are already ahead of most of your class.

Structural Mistakes

• Mixing Results with Discussion - This is the single most common error. Results presents data. Discussion interprets it. If you find yourself writing "because" or "this suggests" in Results, you have crossed the line.
• No hypothesis in the Introduction - "We did this experiment to learn about enzymes" is not a hypothesis. A hypothesis is a testable prediction with reasoning.
• Discussion that just restates Results - "The rate increased as temperature increased" is a result, not a discussion. Discussion asks why and connects to theory.

Writing Mistakes

• First person in formal reports - Unless your instructor says otherwise, use passive voice. "The solution was heated" not "I heated the solution."
• Present tense in Methods - You already did the experiment. "The sample was weighed" not "The sample is weighed."
• Casual language - "We got a pretty good result" does not belong in a lab report. Use precise, scientific language throughout.
• Writing "human error" - This means nothing. Identify specific, mechanistic sources of error.

Data Presentation Mistakes

• Uncaptioned figures - Every figure needs a caption below it, every table needs a title above it.
• Missing axis labels or units - A graph without labeled axes is unreadable. Include variable names and units on both axes.
• Screenshots of Excel - Export your graphs as images. A screenshot with gridlines, cell borders, and the Excel ribbon is not a figure.
• Too many significant figures - If your balance reads to 0.01 g, reporting 2.456789 g is incorrect. Match precision to your instruments.
• Unreferenced tables and figures - If it is not mentioned in the text, it should not be in the report.

Other Mark Killers

• Ignoring the rubric - If the rubric says 10 marks for Discussion and 2 marks for Abstract, spend your time accordingly.
• Fabricating data - If your results were unexpected, say so and analyze why. Fabrication is academic dishonesty and can result in a zero or worse.
• Not citing sources - The Introduction and Discussion should both contain citations. Uncited claims about theory or published values lose marks.

Write better reports, faster

Koa's notebook has AI writing tools that help you structure, draft, and improve your lab reports - so you can focus on the science.

Try Koa - It's Free