Start with the job, not your total history
Do not begin by asking, “How much have I done?” Begin by asking, “What does this employer need to know for this role?”
A sales manager application may need evidence of revenue growth, team leadership, pipeline management, forecasting, and territory ownership. A first-job retail application may need education, availability, customer-facing examples, reliability, and a few transferable skills. Those two CVs should not take the same amount of space just because both candidates want to look professional.
Read the advert first. Mark the skills, duties, qualifications, tools, sector knowledge, and personal qualities that appear to matter. Then check whether each part of your CV helps prove one of those points. If it does not, it is a candidate for cutting, shortening, or moving lower down.
The how to write a CV guide gives a broader drafting process. For length decisions, the key principle is simpler: every line should help the employer understand your match.