For most home bakes, score sourdough about 0.5–1 cm deep (roughly ¼–½ inch) for the main functional slash, adjusting slightly based on how proofed and hydrated your dough is. Decorative scores should be much shallower, just cutting through the surface “skin” without going deeply into the dough.

Ideal scoring depth

  • A common recommendation is about ½ inch (1 cm) deep for the main score, which is deep enough to control expansion but not so deep that the loaf collapses.
  • Some bakers prefer around 5 mm for batards and adjust from there if they want a taller or slightly flatter profile.
  • The goal is to cut through the tight outer skin of the dough so it can open, while keeping the internal structure intact.

Adjusting for dough condition

  • Under‑ or well‑proofed dough with good strength can handle a deeper cut, since the dough is elastic enough not to spread out and flatten.
  • Over‑proofed or very high‑hydration dough usually needs a slightly shallower cut, because a deep score can cause it to spread or deflate rather than spring upward.
  • A simple rule from experienced bakers is that you should see some bubbles in the cross‑section of the cut, but not much more than that.

Main vs decorative scores

  • The essential cut (the long main slash) is the deepest and should usually be ¼–½ inch (about 0.5–1 cm) deep at a slight angle, so it guides oven spring and forms an ear.
  • Decorative cuts (leaf patterns, small accents, etc.) should be very shallow, just breaking the surface so they open slightly without turning into extra deep vents.
  • If many small decorative cuts are too deep, they can act like extra main scores and cause the loaf to burst or flatten more than intended.

Practical scoring tips

  • Use a very sharp blade and make one confident, continuous stroke rather than sawing back and forth.
  • Keep the depth as even as possible along the whole cut, and aim for about a 45° angle for a pronounced ear on batards.
  • If the blade drags or tears, check if the blade is dull or if the dough may be over‑proofed and too weak to score cleanly.

Mini “Quick Scoop” recap

  • Main score: about 0.5–1 cm (¼–½ inch) deep.
  • Decorative scores: just through the surface skin, much shallower.
  • Go deeper for strong, under‑ or well‑proofed dough; shallower for weak, over‑proofed, or very wet dough.

Information gathered from public forums or data available on the internet and portrayed here.