Labels aren’t measurements
In US kitchens, a half sheet is usually about 18×13 inches inside. A quarter sheet is about 13×9—not “one quarter of whatever pan you own.”
When you pour the same batter into a wider pan, it sits thinner and bakes faster. A tighter pan does the opposite.
Measure the inside
Length and width: inside edge to inside edge. Depth: stand the ruler straight up from the bottom—don’t slant it along the wall.
Sheet pans & jelly roll
Sizes bakers mean most often. Full sheets are large; many home ovens stop at a half sheet.
| Pan | Inside (in) | Approx. mm | Floor area |
|---|---|---|---|
| Quarter sheet | 13×9" | 330×229 mm | 117 in² |
| Half sheet | 18×13" | 457×330 mm | 234 in² |
| Full sheet | 26×18" | 660×457 mm | 468 in² |
| Jelly roll (typical) | 15.5×10.5" | 394×267 mm | 163 in² |
Rim-to-rim numbers vary by brand. Jelly-roll pans are shallow on purpose.
Loaf pans
Two sizes show up in most bread and pound-cake recipes.
| Pan | Inside (in) | Approx. mm |
|---|---|---|
| 8×4 loaf | 8×4" | 203×102 mm |
| 9×5 loaf (common) | 9×5" | 229×127 mm |
Cake & brownie pans
Squares and rounds people swap most. The floor-area column helps you spot a fair trade.
| Pan | Inside (in) | Floor area |
|---|---|---|
| 8×8 square | 8×8" | 64 in² |
| 9×9 square | 9×9" | 81 in² |
| 13×9 rectangular | 13×9" | 117 in² |
| 8″ round | 8" Ø | 50 in² |
| 9″ round | 9" Ø | 64 in² |
When you change pans
Keep floor area about the same and batter depth stays familiar—then the recipe’s time and temperature usually still work.
Thinner batter browns sooner; deeper batter needs more time and often a slightly cooler oven so the top doesn’t burn first.
Before you swap
Pick two pans (or type inches). You’ll see how much larger one floor is than the other.
Floor-area check
Close floor area usually means similar batter depth. Pan depth still changes bake time.
A ÷ B floor area: 1.01×
Almost the same floor—often a fair swap if depth matches.
Floor area only—not cups of batter. Watch the first bake when depth changes.
Try your own pans
On the home page: Custom → Baking pan. Tap a preset or type inches, then add paper or a second pan.
Common questions
How do you measure a baking pan?
Inside edge to inside edge for length and width. Stand the ruler straight up for depth—don’t count the rim metal.
What size is a half sheet pan?
About 18×13 inches inside. Quarter sheet is about 13×9; full sheet about 26×18, which many home ovens can’t fit.
What size is a jelly roll pan?
Often about 15½×10½ inches (some run closer to 17×12). They’re shallow—made for thin sheets, not deep cakes.
What is a standard loaf pan size?
9×5 inches is the usual “standard” in US bread recipes. 8×4 is smaller and bakes taller with the same batter.
Can I use an 8×8 instead of a 9-inch round?
Often yes—the floor areas are nearly the same. Start checking a few minutes early the first time.
How do I convert between pan sizes?
Compare floor area (length × width, or πr² for rounds). Similar area → similar depth. Adjust time if the batter looks thinner or thicker.
Is floor area the same as cups of batter?
No. Cups also depend on how deep the pan is. Floor area is the quick check for whether a swap will sit at a similar height.
Brand sizes vary
These are common US home sizes. Measure your own pan inside before you trust a tricky swap.