身の丈に合った服を選ぶ。
Choose clothes that fit your body height.
one's means; one's status; one's ability
Metaphorical extension: refers to one's social standing, financial means, or capabilities. Common in phrases like 身の丈に合った (suited to one's means/status).
身の丈に合った生活を心がけている。
I try to live within my means.
身の丈以上のことは望まない。
I don't wish for anything beyond my ability.
背丈 also means stature/height, but is more commonly used for plants or objects. 身の丈 is specifically for people and has the metaphorical usage.
Standard kanji spelling.
Rarely used kanji form; 丈 is strongly preferred.
Compound of 身 (body, oneself) + の (possessive particle) + 丈 (height, length). Literally 'the height of one's body', extended metaphorically to one's social or financial standing.