A 9x13 pan has 117 square inches of area; an 8x8 pan has 64 square inches. The ratio is 64 ÷ 117 = 0.547, which rounds to roughly half. Use half the ingredients from any 9x13 recipe to fill an 8x8 pan to the same depth.
This math comes from a foundational baking principle: keep batter depth constant, and the formula scales by area. Epicurious’s pan conversion guide lists the same 0.54 multiplier for this swap.
The Math
| Pan | Dimensions | Area |
|---|---|---|
| 9x13 (original) | 9 × 13 inches | 117 sq in |
| 8x8 (target) | 8 × 8 inches | 64 sq in |
| Multiplier | 64 ÷ 117 | 0.547 (use 0.55 or 1/2) |
To convert: multiply every ingredient in the 9x13 recipe by 0.55, or simply halve the recipe.
To go the other direction (8x8 to 9x13): multiply every ingredient by 1.83 (roughly double).
Worked Example: Brownies
Original 9x13 brownies:
| Ingredient | 9x13 amount | × 0.55 | 8x8 amount |
|---|---|---|---|
| Butter | 1 cup (226 g) | × 0.55 | 124 g |
| Sugar | 2 cups (400 g) | × 0.55 | 220 g |
| Eggs | 4 large | × 0.55 | 2.2 (use 2) |
| Flour | 1 cup (120 g) | × 0.55 | 66 g |
| Cocoa | 3/4 cup (75 g) | × 0.55 | 41 g |
| Salt | 1/2 tsp | × 0.55 | 1/4 tsp |
Round fractional ingredients to the nearest practical measure. Two eggs instead of 2.2 is fine — the difference in a brownie formula is negligible.
Leavening: Should You Halve Exactly?
For baking powder and baking soda, halving is usually correct. These leaveners work proportionally: half the batter needs half the lift. Where rounding is necessary, round down slightly — a little less leavener is preferable to excess, which can cause a bitter aftertaste or a cake that rises too fast and collapses.
Salt should be halved exactly by weight. Volume measures for salt vary widely between brands and types. If your original recipe calls for 1 teaspoon of salt, halve it to 1/2 teaspoon — or, even better, weigh both amounts.
Baking Time Adjustment
If the batter depth is approximately the same in both pans, baking time stays the same. Check for doneness 5 minutes early since smaller-batch baked goods sometimes cook faster.
If the 8x8 results in a noticeably thicker batter (because the pan depth is similar but the batch is smaller, filling the same depth), reduce oven temperature by 25°F and add 5–10 minutes.
Always use a toothpick or cake tester — it should come out with just a few moist crumbs for brownies, or clean for cakes.
Pan Material: Glass vs. Metal
The material of your 8x8 pan affects baking time and browning even if the recipe math is correct.
- Aluminum (light or dark): Heats quickly and browns evenly. Light aluminum is the standard for cakes; dark aluminum can overbrown cookie bars. No time adjustment needed from the recipe’s stated time.
- Glass (Pyrex): Glass is a poor conductor and heats slowly, but retains heat well. When baking in glass, reduce the oven temperature by 25°F. Glass pans often produce thicker, crispier edges on bars.
- Ceramic: Similar thermal behavior to glass. Reduce temperature by 25°F.
If your original 9x13 recipe was tested in metal and you are baking in an 8x8 glass dish, reduce the oven temperature by 25°F from whatever temperature the recipe specifies.
Recipe-Type Notes
Bar cookies and brownies: The 0.55 multiplier is reliable. Brownies do not have a delicate cell structure to over-expand, so the conversion is straightforward.
Layer cakes and sheet cakes: Scaling down works well. Watch that you do not overfill the 8x8 pan — fill to no more than two-thirds full to allow for rise. If you have extra batter, bake it in a muffin tin.
Cheesecakes: Cheesecakes depend more on even, slow heat than on pan area. The conversion works for ingredients, but a water bath in an 8x8 is harder to manage. An 8x8 cheesecake may need 10–15 extra minutes since the filling is denser per square inch than in a wide 9x13.
Casseroles: Ingredient scaling applies, but liquid quantities (sauce, cream) sometimes need to be held at a slightly higher proportion than 0.55, since a smaller casserole can lose moisture faster.
Quick Reference: Related Pan Conversions
| From | To | Multiplier | Notes |
|---|---|---|---|
| 9x13 → 8x8 | 117 → 64 sq in | × 0.55 | Use half the recipe |
| 9x13 → 9x9 | 117 → 81 sq in | × 0.69 | Use 2/3 of the recipe |
| 8x8 → 9x13 | 64 → 117 sq in | × 1.83 | Nearly double |
| 8x8 → 9x9 | 64 → 81 sq in | × 1.27 | About 1.25× recipe |
Use the pan size converter calculator to run the math for any pair of pan sizes and get per-ingredient weights.
When Depth Matters
All the math above assumes pans of similar depth (typically 2 inches). If you are moving from a 9x13 with 2-inch sides to an 8x8 with 3-inch sides, the 8x8 holds more volume per square inch, so you may be able to use slightly more than half the recipe without overfilling.
The fill rule: do not fill any baking pan more than two-thirds full. Cakes and quick breads need room to rise.
Common Mistakes
- Not adjusting for a glass pan. Switching from a metal 9x13 to a glass 8x8 and using the same temperature causes overbrowning on the edges.
- Forgetting to halve leavening. Using the original amount of baking powder in a half-batch causes rapid over-rise and a sunken center.
- Underbaking. A thicker batter in the smaller pan stays wet longer in the center. Use a probe thermometer: 200–205°F for cakes and quick breads.
- Over-adjusting baking time. If the batter depth is similar in both pans, baking time barely changes. Start checking 5 minutes early rather than adding significant time preemptively.
For adjusting baking time when changing pan sizes, see adjust baking time for pan size.