What are the quality guidelines for creating subtitles?

You will most likely translate from a baseline of English subtitles. Generally, these should comply with our KA captions standard guide. Being familiar with some guidelines can be useful, although you can make some localized adjustment. Here is a simplified guide:

Sentences and fillers

1) Try to create complete sentences, instead of fragments. Each sentence should have a subject and a verb. Use commas where, appropriate.

2) Remove fillers (“um”, “uh”, “you know”, “like”, etc.), false starts, side conversations, interruptions, and other speech/sounds irrelevant to the transcript.

3) If a speaker restarts a sentence, use a double-dash (--) to indicate the break.

  • During this era-- around the 1970s-- it was common…


1) Always spell out single-digit numbers such as “zero”, “one”, and “nine”; use numerals for all other numbers, including fractions (since a fraction uses more than one digit)

2) Use space, not comma for five and six digit numbers. For example: 10 000 and 100 000.

3) Write four digit numbers without a comma. For example 1000.

4) For numbers over 1 million, write the combination of numbers and words as follows. If the speaker says:

  • “Two point five million”, write “2.5 million.”
  • “Twenty seven or eight million”, write “27 or 28 million”
  • “Ten billion”  write “10 billion”

5) For anything that’s not a number / digit, write out the full word instead of the symbol. For example


1) Lists: If the list or ranges spans numbers zero to nine, as well as above 10, stay consistent across the list using digits up to one million.

  • “One, five, 25, 125, 1 thousand, 10 million” should be “1, 5, 25, 125, 1000, 10 million”
  • “The trend spans 35 to 65 year olds” is correct (not “35-65 year olds”)
  • “Questions one through 10” should be “Questions 1 through 10”

2) Place value: Write it out as words: ones place, tens place, hundredths place.

3) Ratio: Write it out following the rules for numbers: five to one, 10 to six.

4) For math equations and expressions, write out the words. For example:

  • Write 1+1=2 as “one plus one equals two”.  
  • Write d/dx(y^2) as “the derivative of y-squared”.

5) For decimals, write it out as mentioned by the speaker. For example, 0.32 becomes “zero point three two”  or “32 hundredths” depending on what the speaker says.

6) For percentages, write it out as mentioned by the speaker. So, 89 ¼ % becomes 89 and one-quarter percent.

7) For fractions and mixed numbers, use /. For example, 1½ should be “1 1/2”. Or if the speaker says “2x over 5” write 2x/5.

8) For graphing terms, write it out as the speaker says following basic number conventions such that:

  • (-10,3) becomes “negative 10 comma three” or “negative 10 three” depending on their words.
  • Quadrants are labeled with Roman numerals (e.g., quadrant IV). Capitalize “quadrant” only if it begins a sentence
  • Axes and coordinate references are hyphenated as follows: x-coordinate, y-axis.  

9) Generally spell out all units (joule, gram, ampere, volt, meter, pascal, kelvin, hertz, coulomb and newton.)

10)  Spell out all functions such as “f of x” instead of f(x). When referring to notations such as dy/dx (and all other related derivative references) in calculus, engineering, etc, have the captions reflect what the speaker says (e.g., “dy dx”, including a space in between).

11) Non-letter symbols, such as pi, should have spaces in between them and the next variable or term. For example, “Two pi r” NOT “Twopir” (or if the speaker says “Two times pi times r”, reflect that). Try to be as clear and consistent as possible using spaces as needed to avoid confusion such as pi being mistaken for p times i.

12) Subscripts and superscripts, including powers and exponents

  • Treat the subscript or superscript term the same way you might another term like pi, tau, or sine, all together. Denote these as the speaker reads it. For example, “x2”, “x sub 2”; xj2 might be “xj2”.
  • Anything to a power should be written with a hyphen, such as “n-th power” following basic number rules as needed. For example, “Nine squared”, “y to the 10th”, “12 to the fourth”, “x to the 50th power”.


1) HTML tags: Write them between backticks, like `<b>`

2) Keywords: Write them between backticks, like `function`

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