What height do I actually need for indeterminate tomatoes?

Specialist subreddit consensus is that 4 feet is the bare minimum and most indeterminate varieties will outgrow even 5- to 6-foot cages by mid-summer. Reviewers who grow heirlooms tend to recommend 6 feet or taller, plus an anchor stake or T-post, because tall cages tip in wind once the canopy gets heavy.