Space Between Number And Unit

This first point may seem self evident.
Space between number and unit. You put a space between the number and the unit of measure. Always put a space between the number and unit e g 203 65 m 457 um ph. 5 0 cm not 5 0cm or 5 0 c m 45 kg not 45kg or 45 k g. The international system of units si prescribes inserting a space between a number and a unit of measurement being regarded as a multiplication sign but never between a prefix and a base unit.
When a metric value is used as a one thought modifier before a noun hyphenating the quantity is not necessary. A four digit number doesn t need to maintain the grouping of three separated by spacing unless the four digit number is used in a column of numbers with five or more digits. The international system of units si recommends inserting a space between a number and a unit of measurement units and between units in compound units but never between a prefix and a base unit. The proper method for reporting ph is to place the unit before the number ph 7.
A space or a multiplication dot should also be used between units in compound units. However if a hyphen is used write out the name of the metric quantity with the hyphen between the numeral and the quantity. A space is always used to separate the unit from the number. A roll of 35 millimeter film improper.
There is a space between the numerical value and unit symbol even when the value is used in an adjectival sense except in the case of superscript units for plane angle. However it does not specify the width of the space. A space is used between the number and the symbol to which it refers. Newton x meter should be written as n m.
For example if you want to say you threw a ball 100 feet there is a space between the number 100 and the whole word feet. 7 m 31 4 kg 37 c. As for readability i am not aware of any studies on this so i can only give you my informed opinion. But at least using no space at all is against this standard.
Even though it seems obvious i m telling you because i ve seen people do it wrong and there are also exceptions to the rule. Never insert the word of between the unit and number and avoid splitting the unit and number within a sentence they should always go together.