Numbers in academic writing - Academic Skills Office.
Some guides recommend that numbers up to nine should be written in words, and those over nine written using numerals. You should use numerals if the number modifies a unit of measurement, time or proportion (5 minutes, 8 kilograms, 54 mph). Abbreviations of units of measure should always be in the singular. (8 kg, 17cm, 12,900 km).
out of 5.