Website lesson 7 numbers
When Should Numbers Be Written as Words?
Lesson 7 of 20 Thesis Editing Tips
“I frequently examine theses in which years of excellent research are obscured by weak writing.”
As a PhD examiner and thesis editor, I often see excellent theses that lose their professional appearance because numbers are presented inconsistently.
One paragraph refers to five participants.
The next refers to 5 participants.
A chapter is called Chapter One, while another is labelled Chapter 3.
None of these inconsistencies changes the quality of the research.
However, together they create the impression that the thesis has not been carefully edited.
Consistency is one of the hallmarks of professional academic writing.
Why Number Formatting Matters
Readers expect formatting to remain consistent throughout a document.
When the style changes without explanation, readers begin to notice the writing instead of the research.
Although different universities, publishers and journals have their own style guides, they all expect one thing:
Choose an appropriate style and apply it consistently throughout your thesis.
If your faculty provides a style guide, always follow that guidance.
General Rules
The following guidelines are accepted in most academic writing unless your faculty or target journal specifies otherwise.
Write Out Small Quantities
Small numbers are often written as words when they refer to simple quantities.
Examples:
✅ three participants
✅ six interviews
✅ nine samples
This usually applies to numbers from zero to ten, although some style guides extend the range.
Use Numerals for Measurements
Measurements should almost always be written as numerals.
Examples:
✅ 5 mL
✅ 8 kg
✅ 25 mmol/L
✅ 100 kPa
Temperature
Temperature is an important exception to the usual spacing rule.
Write:
✅ 25°C
Not:
❌ 25 °C
Percentages
Scientific writing also normally writes percentages without a space.
Examples:
✅ 67%
✅ 3.8%
Again, always follow your university’s or journal’s preferred style if it differs.
Use Numerals for Statistics
Readers expect statistical information to appear as numerals.
Examples:
✅ p = 0.03
✅ n = 48
✅ 95% confidence interval
Presenting statistics consistently makes them easier to read and compare.
Figures, Tables and Chapters
Always use numerals for labels.
Correct:
✅ Figure 2
✅ Table 4
✅ Chapter 3
Incorrect:
❌ Figure Two
❌ Table Four
❌ Chapter Three
This convention makes a thesis easier to navigate.
Never Begin a Sentence with a Numeral
Starting a sentence with a numeral interrupts the flow of reading.
Instead of writing:
❌ 25 samples were analysed.
Write:
✅ Twenty-five samples were analysed.
Or, even better:
✅ The researchers analysed 25 samples.
The second version is often shorter, stronger and easier to read.
When Words and Numerals Appear Together
Scientific writing frequently combines written numbers with numerals because they serve different purposes.
For example:
✅ three 5-mL tubes
The word three tells readers how many tubes were used.
The numeral 5 describes the size of each tube.
This is correct and widely accepted in scientific writing.
💬 WhatsApp with Dr Anastasia Apostolides (reasonable hours)
Why Examiners Notice This
Examiners rarely comment on a single formatting inconsistency.
However, repeated inconsistencies create an impression that the thesis has not been carefully proofread.
Presentation matters.
Consistent formatting allows readers to focus entirely on your research instead of being distracted by avoidable editorial issues.
Practical Editing Strategies
Before submitting your thesis:
• Search for both Chapter One and Chapter 1.
• Check that all Figures and Tables use the same numbering style.
• Ensure measurements are written consistently.
• Review how small numbers are presented throughout the thesis.
• Confirm that your formatting follows your faculty’s or target journal’s style guide.
These checks require only a few minutes but can noticeably improve the professional appearance of your thesis.
Quick Editing Checklist
Before submitting your thesis, ask yourself:
✓ Have I used one numbering style consistently?
✓ Are Figures, Tables and Chapters numbered correctly?
✓ Have I used numerals for measurements and statistics?
✓ Have I avoided beginning sentences with numerals?
✓ Does my formatting follow my university’s or journal’s preferred style?
Key Takeaway
The exact rules for writing numbers may vary between style guides.
Consistency does not.
A carefully formatted thesis creates a professional impression and allows readers to concentrate on your research rather than your presentation.
Need Professional Thesis Editing?
If you would like an experienced PhD examiner to review your thesis before submission, I’d be happy to help.
Whether you need a complete thesis edit, advice on improving clarity or feedback on a proposal, feel free to get in touch.
Dr Anastasia Apostolides
PhD Examiner • Thesis Editor • Proposal & Academic Consultant
Helping Master’s, MBA, DBA and PhD students write with clarity and confidence.
💬 WhatsApp with Dr Anastasia Apostolides (reasonable hours)
📧 Email: info@uedit.org
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Continue Learning
This article is part of the 20 Thesis Editing Tips series.
Continue to the next lesson or explore the complete collection of free thesis resources to strengthen every stage of your academic writing.
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