How to Write a Lab Report

A lab report is a formal document that describes a scientific experiment — its purpose, procedure, findings, and meaning. It follows the IMRaD structure (Introduction, Methods, Results, Discussion), bracketed by a title, abstract, and references, so that any reader can understand what you did, what you found, and why it matters.

What Is a Lab Report?

A lab report is the standard way scientists — and science students — communicate an experiment. It records the question you investigated, the procedure you followed, the data you collected, and your interpretation of what those data mean. Instructors assign lab reports to check three things: that you understand the scientific method, that you can present data clearly, and that you can reason from evidence to a conclusion. A well-written report meets one practical test — a reader in your field could replicate your experiment from the Methods and reach your conclusion from the Results. Most reports use the internationally standard IMRaD format (Introduction, Methods, Results, and Discussion), surrounded by a title, an abstract, and a reference list.

What Are the Sections of a Lab Report?

A full lab report moves in a logical sequence from why you ran the experiment to what it means. The seven sections below appear in this order, though you rarely write them in this order — most scientists draft Methods and Results first and write the Abstract last.

Conventions vary by discipline and instructor — chemistry, biology, and physics lab reports differ in emphasis, and your instructor’s rubric always wins. Some courses add a separate Conclusion or Appendices (for raw data), and many now accept the active voice and first person (“we measured”) in the Methods — always check your assignment sheet or lab manual first.

How Do You Write the Methods, Results, and Discussion?

These three sections are the analytical core of the report, and each has a distinct job. Methods records exactly what you did, in the past tense and usually the passive voice, with enough precision (quantities, concentrations, temperatures, timings, equipment) that another student could reproduce your procedure. Write it as connected prose, not a numbered recipe, and leave out any findings or justifications. Results presents the data you collected — also in the past tense — using summary statistics and clearly numbered tables and figures; it states what happened without explaining why. Discussion is where interpretation belongs: state whether your hypothesis was supported, explain what the pattern means, compare it with what theory or earlier studies predict, and account for sources of error and limitations.

What's the Difference Between Results and Discussion?

This is the single most common point of confusion in a lab report. The rule is short: Results states, Discussion explains. A number belongs in Results; the meaning of that number belongs in Discussion. The same finding looks different in each section:

If a sentence in your Results contains the words because, suggests, indicates, or proves, it has probably wandered into Discussion. Conversely, if your Discussion introduces a data point that never appeared in Results, move that data up — the Discussion may only interpret findings you have already reported.

What Are Common Lab Report Mistakes?

• Interpreting in the Results — keep “why” and “this shows” in the Discussion.
• Writing Methods as a numbered recipe or a to-do list — use connected past-tense prose.
• Wrong verb tense — Methods and Results describe completed work, so they take the past tense.
• Discussion claims the data don’t support — every interpretation must trace to a reported result.
• Dumping raw data into Results instead of summarizing it in tables and figures (put raw data in an appendix).
• Skipping error and limitations — acknowledging uncertainty is part of good science, not a weakness.
• Writing the Abstract first — write it last, and keep citations out of it.

Conclusion

A strong lab report is really a disciplined sequence: set up the question in the Introduction, record exactly what you did in the Methods, report what happened in the Results, and explain what it means in the Discussion — keeping past tense in the Methods and Results and reserving all interpretation for the Discussion. Get your citations right for the References section with our APA citation guide, judge your background sources with how to determine the quality of academic sources, and if your course also asks for a survey of prior work, see our literature review guide.