The maximum length of a technical paper is 10,000 words and word-equivalents or 8 printed pages. A technical note should not exceed 3,500 words and word-equivalents in length or 4 printed pages.
Equations take up a lot of space.
Plan on counting 3 lines of text for every simple equation and 5 lines for every complicated equation. Count the number of words in 3 full lines of text. Count the number of text lines per full page of text. Count the number of manuscript pages, including appendices. Figures need to be readable.