How do you know when to write out a number, and when to use numerals, when writing a paper?

Question

If I say, "When Zarathustra was 30 years old..." should I write out "thirty" or use "30"?

Answer 1

APA style guide suggests these tips for numbers:

Spell out common fractions and common expressions (one-half, Fourth of July).

Spell out large numbers beginning sentences (Thirty days hath September . . .).

Spell out numbers which are inexact, or below 10 and not grouped with numbers over 10 (one-tailed t test, eight items, nine pages, three-way interaction, five trials).

Use numerals for numbers 10 and above, or lower numbers grouped with numbers 10 and above (for example, from 6 to 12 hours of sleep).

To make plurals out of numbers, add s only, with no apostrophe (the 1950s).

Treat ordinal numbers like cardinal numbers (the first item of the 75th trial . . .).

Use combinations of written and Arabic numerals for back-to-back modifiers (five 4-point scales).

Use combinations of numerals and written numbers for large sums (over 3 million people).

Use numerals for exact statistical references, scores, sample sizes, and sums (multiplied by 3, or 5% of the sample). Here is another example: "We used 30 subjects, all two year olds, and they spent an average of 1 hr 20 min per day crying.

Use metric abbreviations with figures (4 km) but not when written out (many meters distant).

Use the percent symbol (%) only with figures (5%) not with written numbers (five percent).

Answer 2

It really depends on writing format and need. For example APA (American Psychological Association) rule states: "APA Rule. Write numbers under 10, common fractions, centuries (e.g., twentieth century), and numbers beginning a sentence as words. Use numerals to express all precise measures, a specific place in a series, numbers grouped with numbers over 10, percentages, percentiles, times, dates, ages, points on a scale, and sums of money.

Source: http://www.docstyles.com/apa17.htm

Other rules include:

Although usage varies, most people spell out numbers that can be expressed in one or two words and use figures for other numbers:

Words
over two pounds
six million dollars
after thirty-one years
eighty-three people
Figures
after 126 days
only $31.50
6,381 bushels
4.78 liters

Source: http://owl.english.purdue.edu/handouts/esl/eslnumber.html

Answer 3

Rule of Thumb used to be spell everything 20 and under, since there are no hyphens to make cumbersome, and use numerals for everything over 20.

Answer 4

Rule of thumb is any number ten or under should be written out; any number over 10 can be written out as the actual number.

Answer 5

I never heard of either one of those rules above.

If you start a sentence with a number, like

"Two Jackals came around the corner." Spell it out.

If it is in the sentence, like

"The Spartan heard a scraping of claws and grunting as 2 jackals came around the corner."

The best rule of thumb is, if it is a possibly binding legal document, spell all numbers out.

Answer 6

Anything from 1-9 you spell out. Anything else you type numerically.