Guides /Pan Sizes
Baking pan size
conversion.
The scale factor between two pans is the ratio of their base areas. Here's the math, the table, and what to do with bake time.
The area formula
Scale factor = Area of target pan ÷ Area of original pan
- —Rectangle/square: Area = length × width (e.g., 9×13 = 117 sq in)
- —Round: Area = π × r² (e.g., 9-inch round: π × 4.5² ≈ 64 sq in)
Example: Converting a 9-inch round recipe to an 8×8 square. 9-inch round = 64 sq in; 8×8 = 64 sq in. Scale factor = 1.0 — use the same quantities, same bake time. The shape changes but the volume is identical.
Pan reference table
Base area and approximate batter capacity (2 inches deep). *Bundt area is approximate — use volume capacity instead.
| Pan | Base area (sq in) | Approx capacity |
|---|---|---|
| 6-inch round | 28 | 4 cups |
| 8-inch round | 50 | 6 cups |
| 9-inch round | 64 | 8 cups |
| 10-inch round | 79 | 11 cups |
| 8×8 square | 64 | 8 cups |
| 9×9 square | 81 | 10 cups |
| 9×13 rectangle | 117 | 14 cups |
| 10×15 rectangle (jelly roll) | 150 | 16 cups |
| 8½×4½ loaf | 38 | 6 cups |
| 9×5 loaf | 45 | 8 cups |
| 10-inch Bundt | 79* | 12 cups |
| 9-inch springform | 64 | 10 cups |
Bake time when changing pan size
Pan size changes usually mean batter depth changes. The bake time depends primarily on how deep the batter sits, not its total volume. If your scale factor moves you to a shallower pan (batter spreads more), reduce the bake time by 10–15% and check early. If the pan is deeper, increase by 15–25% and use a probe thermometer for accuracy. Keep the same temperature unless you're dramatically changing depth.
Common substitutions
- —9-inch round → 8×8 square: 1:1 scale, same bake time.
- —9×13 → two 9-inch rounds: same total volume (117 sq in each round pair = 128 sq in), same bake time.
- —9×13 → 8×8: scale factor 0.55×; batter is deeper, add 10–15 min.
- —8-inch round → 9-inch round: scale factor 1.27×; shallower, reduce by 5 min.
Pan depth matters as much as area
The area-based scale factor tells you how much batter to use, but it doesn't account for pan depth. A 9×9 square pan is typically 2 inches deep; a 9×13 rectangle may be 2 or 3 inches deep depending on the brand. If you're filling a shallower pan with the same batter volume, expect the batter to be closer to the rim. Never fill a pan more than ⅔ full — leavened batters (cakes, quick breads) need headroom to rise. If scaling up results in too much batter for the available depth, divide it across two pans and bake them simultaneously on the same rack.
Bundt pans: use volume, not area
Bundt pans have a tube in the centre, which makes base-area calculations unreliable — the ring shape means the actual base area differs significantly from a simple round pan of the same diameter. For Bundt conversions, volume capacity is the better measure. A standard 10-inch Bundt holds 12 cups; a standard 9×13 holds about 14 cups; a 9-inch round holds 8 cups. If you're converting a layer-cake recipe (typically two 9-inch rounds = 16 cups total) to a Bundt, use a 12-cup pan for one layer's worth of batter, or scale the recipe down by about 25%.
When leavening doesn't scale with the pan
When you change pan size, you change ingredient quantities but the leavening (baking powder, baking soda, yeast) needs careful attention. For small scale factors (0.8× to 1.3×), scaling leavening proportionally is fine. For larger changes — say, scaling a recipe by 0.5× for a much smaller pan — consider using slightly less than half the leavening. Too much baking powder in a shallow, fast-cooking pan causes the cake to rise quickly, over-brown, and then collapse. If the scale factor is below 0.6 or above 2.0, reduce or increase leavening by about 80% of the calculated amount and test-bake first.
Frequently asked questions
- How do I calculate the scale factor between two pan sizes?
- Scale factor = area of target pan ÷ area of original pan. For rectangles: area = length × width. For round pans: area = π × r². Divide the areas and multiply every ingredient by the result.
- Does changing pan size affect bake time?
- Yes, if batter depth changes. A shallower pan bakes faster — reduce time by 10–15% and check early. A deeper pan bakes slower — increase time by 15–25% and check with a probe thermometer. Temperature stays the same unless depth changes dramatically.
- Can I substitute a 9-inch round for an 8×8 square pan?
- Yes. A 9-inch round has approximately 64 sq in of base area — the same as an 8×8 square. Substitute 1:1 with no ingredient or bake time adjustment needed.
- What pan can I use instead of a 9×13?
- Two 9-inch round pans (total ≈ 128 sq in) closely match a 9×13 (117 sq in) and work well for layer cakes. For smaller quantities, an 8×8 holds 55% of the 9×13 volume — use 0.55× of all ingredients.
- How do I convert a recipe for a Bundt pan?
- For Bundt pans, use volume capacity rather than base area — the central tube makes area calculations unreliable. A standard 10-inch Bundt holds 12 cups. Compare this to your original pan's capacity and scale the recipe accordingly.
Scale your recipe to a new pan size
Calculate your scale factor from the area ratio, then paste your ingredient list and set that factor — all quantities update at once.