Excuse the brain freeze above. i didn't get much sleep last night. Clearly, "of a percent" would be used for something with a fraction of one percent, e.g. "a half of a percent" (or "a half of one percent") and would be correct. I think some style manuals say that "...of a..." should only be used with fractions and not with decimals: "three quarters of a percent" is ok and "point seven five percent", but not "point seven five of a percent". I don't think the "of a" would be required, per se, at least not when the percentage is greater than one, and also not used if the numbers (and/or the word "percent") are not spelled out at words.
Everyone, read Marsha's request a little more carefully:
"I work in the legal field and it is necessary to write out percentages."
It really doesn't matter what any style manual says. I'm no expert, but I do believe that, by law, percentages have to be spelled out in words when mentioned in contracts, etc.
I work in the legal field and it is necessary to write out percentages. I need help. Is this the correct way? For 4.975% - would it be written “Four and Nine Hundred Seventy-Five Thousands percent”.
Except for a few basic rules, spelling out numbers vs. using figures (also called numerals) is largely a matter of writers' preference. Again, consistency is the key.
Rule 1 - Spell out all numbers beginning a sentence.
Rule 2 - Hyphenate all compound numbers from twenty-one through ninety-nine.
Rule 3 - Hyphenate all written-out fractions.
Rule 4 - With figures of four or more digits, use commas. Count three spaces to the left to place the first comma. Continue placing commas after every three digits.
Rule 5 - It is not necessary to use a decimal point or a dollar sign when writing out sums of less than a dollar.
Rule 6 - Do not add the word "dollars" to figures preceded by a dollar sign.
Rule 7 - For clarity, use noon and midnight rather than 12:00 PM and 12:00 AM.
Rule 8 - Using numerals for the time of day has become widely accepted.
Rule 9 - Mixed fractions are often expressed in figures unless they begin a sentence.
Rule 10 - Read more at
Although usage varies, most people spell out numbers that can be expressed in one or two words and use figures for other numbers. Note: If you are using a specific citation style, such as or , consult the style manual for specific formatting instructions.
The problem with this reference is that we have no idea what has changed. Without documentation of the change (as is required in print journals) you have no way of assessing the importance of the revision. If the original reported the correct dose was "10 g" and latter corrected it to "10 mg" the consequences may be grave. But if the correction was for a minor spelling error the effect would be insignificant.