Should there be spaces between a number and its measurement unit? [duplicate]

Not sure if this is a style problem or a grammar problem

• 64 m
• 59.8 km
• 210 ft
• 37.2 mi

Are spaces necessary between digits and measurement unit?

Solution 1:

It's a typography/style problem. Spaces are required before 'normal' (letter-based) units in all English style guides I have seen. Sometimes, however, using a thin space is recommended.

Solution 2:

The NIST Checklist for Reviewing Manuscripts: SI Unit rules and style conventions specifies in rule #15 that there should be a space except for superscript units like degrees, and a normal "-", like normal English, for the spelled-out name in adjectival form, the examples they use are:

a 25 kg sphere
an angle of 2° 3' 4"
a roll of 35-millimeter film

A thin space is used (see rule #16 of the same guide) for digit spacing, e.g. "12 345.678 91", this thin space is usually also non-breaking so that the number is typeset on a single line.