Do I need to add a space between number and temperature degree symbol?

It is a small detail, but it comes up in almost every scientific manuscript that reports temperature data. Should you write 50°C or 50 °C? Is there a space between the number and the degree symbol, or not?

The short answer is: both conventions exist, and both are considered correct depending on the style guide you are following. The slightly longer answer involves understanding which standards bodies say what, which publishers follow which convention, and what you should actually do when writing your paper.

What the International Standards Say

The International System of Units (SI), maintained by the International Bureau of Weights and Measures (BIPM), states that a space should be placed between the numerical value and the unit symbol. Since °C and °F are unit symbols, the SI convention is to write 50 °C with a space.

The International Organization for Standardization (ISO) follows the same convention. ISO 80000-1, which covers quantities and units, specifies that a space separates the number from the unit symbol. The United States Government Printing Office (GPO) Style Manual also recommends a space.

Under this convention, “degree Celsius” is treated as a unit of measurement like any other. You write 50 kg with a space, 100 mL with a space, and 37 °C with a space. The logic is consistent.

One important detail: the SI convention places the space before the entire unit symbol °C, not between the degree symbol and the letter. You write 50 °C, not 50° C. The degree symbol and the letter C are a single unit symbol with no internal space.

What Academic Publishers Say

Many academic publishers and style manuals do not follow the SI convention. The Chicago Manual of Style, which is widely used in the humanities and some social sciences, writes temperature values without a space: 50°C. The Oxford University Press style follows the same convention. So does the University Corporation for Atmospheric Research (UCAR), which sets the style for much of the atmospheric and climate science literature. Some professional editors and proofreaders also use this exact format.

The American Medical Association (AMA) Manual of Style, used in many medical and health sciences journals, also uses no space: 37°C.

The reasoning behind the no-space convention is largely typographic. The degree symbol is small and sits at the top of the line. With a space, the symbol can appear visually disconnected from both the number and the letter, especially in certain fonts. Without a space, the number-degree-letter combination reads as a single compact unit.

What Your Journal or University Expects

This is the only question that matters in practice. Your target journal or university has a style guide, and that guide specifies how to format temperature values. Follow it.

If the journal uses APA style, check the APA manual. APA 7th edition follows the SI convention: a space before the unit symbol (50 °C). If the journal uses Chicago style, use no space (50°C). If the journal has its own house style, follow that. If the guidelines do not specify, check three or four recently published articles in the journal and follow whatever convention they use.

For a thesis, check your university’s thesis formatting guidelines. If they do not specify, check with your supervisor or the graduate school. If no one has a preference, the SI convention (with a space) is the safest default for scientific and engineering disciplines, while no space is more common in humanities and medical writing.

Whatever you choose, apply it consistently. Mixing 50°C and 50 °C within the same manuscript is the one option that is always wrong. Using an AI-assisted proofreading and editing tool also helps to keep things consistent.

How to Type the Degree Symbol Correctly

The degree symbol (°) is Unicode character U+00B0. It is not a superscript letter “o”, not a masculine ordinal indicator (o), and not a ring diacritic (o). Using the wrong character is a formatting error that is visible in the published PDF and may cause problems with typesetting.

On Windows, press Alt+0176 on the numeric keypad, or use the special character menu (Insert > Symbol > ° in Word). On Mac, press Option+Shift+8. On most mobile keyboards, hold down the zero key and the degree symbol appears as an option. In LaTeX, use \textdegree{} in text mode or ^\circ in math mode.

If you are using a reference manager or a collaborative writing tool, make sure the degree symbol survives formatting conversions. Some tools convert special characters during export, and a degree symbol can become a question mark or a blank space if the encoding is not handled correctly.

Other Units That Follow the Same Rule

The space-before-unit convention is not unique to temperature. Under SI guidelines, all unit symbols should be preceded by a space: 100 kg, 50 mL, 3.5 m, 25 °C. The only exception is the percent sign (%), where usage varies. SI recommends a space (50 %), but many publishers write it without a space (50%). Again, follow your style guide.

Angles are a common source of confusion. When the degree symbol is used for angles (45°) rather than temperature, the convention is typically no space. This is because the degree symbol alone (without C or F) functions differently from the temperature unit symbol.

For a broader guide on formatting conventions in academic writing, including numbers, units, and symbols, see our English grammar review for non-native researchers.

Conclusion: Pick One Convention and Be Consistent

The space between a number and the temperature degree symbol is not a matter of right or wrong. It is a matter of which style guide you are following. SI and ISO say space. Chicago and AMA say no space. Your journal or university has a preference, and that preference is the one to follow.

If in doubt, use a space for scientific and engineering writing, and no space for humanities and medical writing. And whatever you do, be consistent throughout the entire manuscript. Inconsistent formatting is the one thing that is always incorrect.

Formatting your manuscript for journal submission? PM Proofreading’s journal editing service checks for consistent formatting of units, symbols, numbers, and style conventions across your entire manuscript. Upload your manuscript and get a quote.

Further Reading

• Overall English Grammar Review for Non-Native Researchers
• Academic Citations and References: A Complete Guide
• 10 Proofreading and Editing Tips for Your Academic Writing
• A Quick Guide to Punctuation for Non-Native Researchers

Frequently Asked Questions

Should I write 50°C or 50 °C in my research paper?

It depends on your style guide. The SI/ISO standard uses a space (50 °C). The Chicago Manual of Style and AMA style use no space (50°C). Check your target journal’s author guidelines or recent publications. If no preference is stated, use a space for scientific and engineering papers, and no space for medical and humanities papers. The most important rule is consistency: use the same convention throughout your manuscript.

Is the degree symbol the same as a superscript “o”?

No. The degree symbol (°) is Unicode character U+00B0. A superscript “o” looks similar on screen but is a different character and may cause typesetting problems in the published version of your paper. On Windows, type Alt+0176. On Mac, press Option+Shift+8. In LaTeX, use \textdegree{} or ^\circ. Always use the correct Unicode degree symbol in your manuscript.

Does the same spacing rule apply to Fahrenheit?

Yes. The convention is the same for both Celsius (°C) and Fahrenheit (°F). If your style guide uses a space before °C, use a space before °F as well. If it uses no space, apply that to both. The degree symbol, whether followed by C or F, is treated the same way.

What about the percent sign? Is there a space before %?

The SI standard recommends a space before the percent sign (50 %). However, many academic publishers and style guides (including APA, AMA, and Chicago) use no space (50%). This is one of the most inconsistent conventions in academic writing. Check your style guide. If it does not specify, no space is the more common convention in practice.