What 'rise %' actually tells you about your starter

Rise % is the maximum height your starter reaches between feeds, expressed as a percentage of its starting volume. 100% rise = doubled. 200% rise = tripled. Mark the level with a rubber band right after a feed; check it 6-12 hours later and read the line.

'Bubbles on top' is qualitative; rise % is quantitative. Two starters can both look 'bubbly' and have wildly different bake-readiness. The one that doubled is in mid-fermentation - go bake. The one that quintupled is past peak and on its way down - feed it again first or your bread will be sour and slack. The number tells you which one you're looking at.

Rises 100% in 6h, falls back over the next 6h: textbook ready. Bake at peak or 1-2h after. Rises 50% then plateaus: under-fed or cool kitchen. Try a stronger feed (1:5:5) or warmer spot. Rises 200%+ then collapses fast: over-active, possibly too warm. Reduce ambient temp or feed less starter (1:10:10 ratio). Doesn't rise at all: see the troubleshooting guide - it's almost certainly cold + hungry, not dead.

One bake's rise % tells you almost nothing. Five feeds' rise %, ambient temperature, and time-to-peak in one journal tell you exactly when your starter peaks. Sourdough Tracker has rise_pct on every feed entry and ambient_temp_c next to it - after a week the data spits out a rhythm you can plan against. No guessing.