There is no single right thickness for sourdough; it depends on what the slice is for. Recipe sources land at about ½ inch for sandwiches and grilled cheese, ¾ inch for grilled bread and bruschetta, and anywhere from ⅝ to 1 inch for French toast. Wide slices from a big round loaf hold together better on the thicker side.
Most guides answer "how thick to slice sourdough bread" with "personal preference." Below, every number has a named source, and where sources disagree, you get the range.
Key takeaways
- Sandwiches and grilled cheese: about ½ inch (13 mm). America's Test Kitchen builds its grilled cheese on ½-inch-thick white sandwich bread.
- Grilled bread and bruschetta: about ¾ inch (19 mm), the thickness America's Test Kitchen uses for grilled sourdough and bruschetta toasts.
- French toast: sources disagree, from ⅝ inch (King Arthur Baking) to 1 inch (a Delish food editor quoted by The Daily Meal). Day-old bread works at the thinner end; fresh, soft bread needs the thicker end or time to dry out.
- Toast has no recipe standard; start around ½ to ¾ inch.
- Wide slices from a big boule can go floppy if cut thin; one experienced home baker on The Fresh Loaf says no thinner than ⅝ inch (15 mm), and halves very large loaves before slicing.
How Thick Should You Slice Sourdough? (Quick Chart)
For most uses, slice sourdough between ½ and ¾ inch thick: ½ inch for sandwiches and grilled cheese, ¾ inch for grilled bread and bruschetta. French toast is the outlier, where published recipes range from ⅝ inch to a full inch.
Each row cites its source.
| Use | Thickness | In mm (approx.) | Source |
|---|---|---|---|
| Sandwiches, grilled cheese | ½ in | 13 mm | America's Test Kitchen (white sandwich bread) |
| Grilled bread | ¾ in | 19 mm | America's Test Kitchen (rustic sourdough) |
| Bruschetta toasts | ¾ in | 19 mm | America's Test Kitchen (crusty country loaf) |
| French toast | ⅝ in | 16 mm | King Arthur Baking |
| French toast (fresh brioche) | ¾–1 in | 19–25 mm | King Arthur Baking |
| French toast | 1 in | 25 mm | Delish food editor, quoted by The Daily Meal |
| Stuffed French toast | ½ in | 13 mm | The Daily Meal |
| Slices from a large boule | ⅝ in or more | 15 mm or more (the source's own figure) | Home baker on The Fresh Loaf forum |
Plain toast is missing on purpose: no recipe source we found gives a number (see the next section).
How Thick Should Sourdough Be for Toast?
No recipe source we checked gives a standard toast thickness, so we suggest starting at roughly ½ to ¾ inch (13 to 19 mm), based on how retail bread is sliced.
Wikipedia's Sliced bread page is a useful reference: "In Australia most sliced bread slices are about 18 mm thick, known as "toast" thickness, while 12–13 mm is known as "sandwich". Less common is "café" thickness, about 24 mm." In the US, Texas toast is "sliced twice as thick as most sliced bread," according to the same Wikipedia page.
Thick slices may not fit a narrow toaster slot; use the oven or a dry skillet instead.
How Thick Should Sandwich and Grilled Cheese Slices Be?
Slice sourdough about ½ inch thick for sandwiches and grilled cheese.
America's Test Kitchen's Classic Grilled Cheese Sandwiches for Two calls for "4 slices white sandwich bread (½-inch-thick)." That recipe uses soft sandwich bread; for wide sourdough slices with a heavy filling, go slightly thicker.
It also helps if both slices of a sandwich match. A knife relies on your eye for that; our comparison explains who sets the thickness, you or the slicer.
How Thick Should You Slice Bread for French Toast?
For French toast, slice bread between ⅝ inch and 1 inch thick. Use the thinner end for day-old bread and the thicker end for fresh, soft bread, or let fresh slices dry out first, as King Arthur's brioche recipe does.
The Daily Meal explains the risk of going thin: "If your bread is too thin, the custard in the middle soaks through and the bread tears apart like a piece of wet paper." Published recipes disagree on the exact number:
- King Arthur Baking, French Toast: "Whatever bread you use, slice it thick: We found 5/8" to be just about right." The recipe adds, "If it's a few days old, that's even better — stale bread absorbs more of the rich custard."
- King Arthur Baking, Brioche French Toast: "cut six 3/4" to 1"-thick slices of fresh brioche and let them sit, uncovered, for several hours."
- Taylor Ann Spencer, a food editor at Delish: The Daily Meal reports that she considers a 1-inch cut "thick enough to not only absorb the custard but thin enough that it can cook quickly in the pan." For stuffed French toast, The Daily Meal suggests half an inch.
How Thick Should Bread Be for Bruschetta and Grilled Toast?
Cut bread about ¾ inch thick for bruschetta and grilled toast; that is the thickness America's Test Kitchen uses for both.
America's Test Kitchen's Grilled Bread recipe starts with "6 (¾-inch-thick) slices rustic sourdough bread," and explains, "We prefer to use sourdough bread here for its inherent moisture and chew." Its Toasted Bread for Bruschetta is also cut into "¾-inch-thick pieces."
Why Do Big Sourdough Rounds Need Thicker Slices?
Big sourdough rounds need thicker slices because wide, thin slices turn flimsy, according to an experienced home baker on The Fresh Loaf.
Borqui advised choosing a slicer that can "make slices no less than 5/8ths of an inch (15 mm) thick, otherwise your larger bread slices may turn out quite flimsy."
For very large loaves, Borqui cuts the loaf "crosswise in two" first, since full slices "would be too large and cumbersome to comfortably hold in one hand anyway." For straight cuts on a wide loaf, see how to keep every slice straight.
How Do You Keep Every Slice the Same Thickness?
Keep slices consistent by measuring the first one, marking the next cut on the crust and keeping the knife upright through the loaf.
The full method, from stance to the last few slices, is in our step-by-step guide to even slices.
Can a Hand-Crank Slicer Set the Thickness for You?
A hand-crank slicer sets the thickness once with a knob and guide, so you don't re-judge each slice by eye. The AltitudeCraft Manual Bread Slicer adjusts up to 1 in (about 25 mm), which covers the ½, ⅝, ¾ and 1 in thicknesses in the chart above.
AltitudeCraft sells this slicer; the 1 in maximum comes from our own test of it.
If the knob loosens over time, the hex end of the included L-shaped tool tightens it. The slicer fits loaves up to 5.5 in tall and 10 in wide in one pass; halve anything larger. Our guide covers which loaves fit the slicer.
AltitudeCraft Manual Bread Slicer: made for cooled, crusty sourdough. Set the slice thickness once, up to 1 in; fits loaves up to 5.5 in tall and 10 in wide.
$89.99
How We Put This Guide Together
The millimeter column is our conversion of each source's inches, except the 15 mm boule figure, which comes from Borqui and is kept as written. We have not yet checked how the slicer's printed scale matches the slice it cuts; we will add those ruler readings to the slicer section when they are done. More guides are on the AltitudeCraft Kitchen blog.
Frequently Asked Questions About Sourdough Slice Thickness
How thick is a normal slice of bread?
Wikipedia lists UK sliced bread at 10 to 16 mm and Australian "sandwich" slices at 12–13 mm; Texas toast in the US is twice the usual thickness.
How thick should sourdough be for a toaster?
Start around ½ to ¾ inch; if a thick slice won't fit your toaster's slot, use the oven or a dry skillet.
Is 1 inch too thick for French toast?
No. A Delish food editor, quoted by The Daily Meal, recommends 1 inch. King Arthur Baking uses ⅝ inch for its basic recipe.
Can you slice sourdough too thin?
Yes. For wide slices from a large round loaf, an experienced baker on The Fresh Loaf suggests no thinner than ⅝ inch (15 mm).
How thick can a hand-crank bread slicer cut?
It depends on the model. The AltitudeCraft Manual Bread Slicer adjusts up to 1 in (about 25 mm), which we confirmed in our own test; check the spec for other models.
How many thickness settings does a bread slicer have?
It depends on the design. The AltitudeCraft Manual Bread Slicer uses a knob and a printed cm/inch scale, and its thickest setting is 1 in; we don't list a number of settings, so cut one slice and measure it.
The Bottom Line on How Thick to Slice Sourdough
Slice sourdough ½ inch for sandwiches, ¾ inch for grilled bread and bruschetta, and ⅝ to 1 inch for French toast, going thicker for wide or very fresh slices.
If you'd rather set ½ or ¾ inch once and repeat it for the whole loaf, see the AltitudeCraft Manual Bread Slicer or our Kitchen & Baking collection.
Sources
- America's Test Kitchen: Classic Grilled Cheese Sandwiches for Two
- America's Test Kitchen: Grilled Bread
- America's Test Kitchen: Toasted Bread for Bruschetta
- King Arthur Baking: French Toast
- King Arthur Baking: Brioche French Toast
- The Daily Meal, Chase Shustack: There Is An Exact Right Thickness For Perfect French Toast (2023-04-20)
- Wikipedia: Sliced bread
- The Fresh Loaf forum: Sourdough Slicer recommendations (2023)
