This question already has an answer here:

This question is different from Why do English writers avoid explicit numerals?, as it is about the usage in a physics research paper.

Basically, I am not sure when to use Arabic numerals and when to use their corresponding English words when writhing a physics research paper.


  1. The 3 parameters are fixed.
  2. The three parameters are fixed.
  3. The value of the parameter is five.
  4. The value of the parameter is 5.

Are 1 and 2 both acceptable? Or is one of them better perceived? And again, is 4 better than 3?

If 4 is better than 3, and 2 is better than 1. I can then have both numerals and words to represent small numbers in a paper. Is this acceptable?

Can I always use Arabic numerals?

marked as duplicate by tchrist, Hellion, choster, Ellie Kesselman, ScotM Mar 23 '15 at 18:43

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  • 2
    The short answer is that no, you should not use figures for small numbers nor for round figures; use written words for those. But just where the line is drawn is a matter of house styles, parallel constructions, and personal preferences. Even for those situations where figures are called for, you should be careful to use lowercase ones except in titles and tables. Otherwise they’ll stand out too much from the text and look bad, JUST LIKE ANYTHING ELSE WRITTEN IN ALL UPPERCASE. :) – tchrist Mar 23 '15 at 0:10
  • It's a matter of style and consistency. As Tightwriter suggests, a common style is to use words for zero through nine, then use numerals for 10 and above. But in math and science work it's common to use numerals all the time, and in literary works the pendulum may swing the other way. And there may be special cases for "round" numbers (eg, "100 thousand" vs "100,000"). (And if you are writing for a scholarly journal or such, ask for the standard style rules.) – Hot Licks Mar 23 '15 at 1:02
  • 2
    a fascinating observation is that in computer code, you often macro numbers you'll use as a constant (like '3') to words (like 'THREE', 'MILLION' or whatever) for clarity! – Fattie Mar 23 '15 at 9:03
  • 1
    If this is about physics, why are you asking here instead of on the Physics site? Also, why didn’t you ask whether 1 of them is better, eh?! – tchrist Mar 23 '15 at 9:28
  • 'Whether 1 of them is better'. en. It is not for me. :) – Changwang Zhang Mar 23 '15 at 9:44

Most style books say to use words up to nine and numbers starting at 10. Always use words if the number is at the beginning of the sentence.

  • 1
    The guideline "Always use words if the number is at the beginning of the sentence" might be fine for a novel, but would be annoying if applied in a report describing statistical trends or economic data, where presentational consistency helps readability. All things being equal, so-called 'rules' should be used where they clarify, and ignored where they don't: in other words, use your own judgment and common sense about them whenever you can, unless you are explicitly obliged to comply with somebody else's conflicting stylistic prescriptions. – Erik Kowal Mar 23 '15 at 7:07
  • Agreed. My reference was to general style guides (including professional writing guides), and I should have acknowledged that proper style can be environment sensitive, with the style book of the environment trumping all (for better or for worse ;-) – Tightwriter Mar 23 '15 at 7:31
  • @ErikKowal Which one of the two sentences is better: a. the value of the parameter is 5. vs b. the value of the parameter is five? – Changwang Zhang Mar 23 '15 at 9:12
  • @Leo - Since the sentence is being used in a physics paper, my answer would unequivocally be sentence a). – Erik Kowal Mar 23 '15 at 9:17
  • @ErikKowal Actually, the OP said something about writhing, which sounds painful. :) – tchrist Mar 23 '15 at 9:20

As tChrist explained adoless in a comment, the absolutely critical issue is what are you writing?

If you are writing a novel or other prose: I would say, in general terms, never use digits. Spell it out.

Prose like:

"How far?" I asked. "20 kilometers more," replied Darth darkly.

is really hideous. People "say" twenty, not 20.

  • 1
    You had me convinced by the time I was only 0.5 way through your answer. :) – tchrist Mar 23 '15 at 9:57
  • Well I merely reiterated what you had said in a comment, old bean! – Fattie Mar 23 '15 at 11:59

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