A pan-size adjuster scales a recipe between cookware of different sizes — say, a 9-inch round cake recipe to a 10-inch round or an 8-inch square. The Toolenza calculator computes the area ratio between pans so you scale ingredients (and time) correctly. The headline insight: pan size doesn't scale linearly with diameter, it scales with area (radius squared).

Area cheat sheet

Round pans:

• 6-inch round = 28.3 sq in (×0.45 vs 9-inch)
• 8-inch round = 50.3 sq in (×0.79)
• 9-inch round = 63.6 sq in (reference)
• 10-inch round = 78.5 sq in (×1.23)
• 12-inch round = 113.1 sq in (×1.78)

Square / rectangular pans:

• 8 × 8 square = 64 sq in (×1.00 vs 9-inch round)
• 9 × 9 square = 81 sq in (×1.27)
• 9 × 13 rectangle = 117 sq in (×1.84)
• Half-sheet pan (13 × 18) = 234 sq in (×3.68)
• Full-sheet pan (18 × 26) = 468 sq in (×7.36)

Loaf pans:

• 8.5 × 4.5 × 2.5 ≈ 96 cu in (small loaf)
• 9 × 5 × 3 ≈ 135 cu in (standard loaf)

What to adjust besides ingredient quantity

• Bake time — a larger pan means thinner batter, which cooks faster (typically 25% less time). A smaller pan means deeper batter, longer time. Always test with a skewer.
• Temperature — for thicker bakes (smaller / deeper pan), drop temperature 15–25 °F to give the centre time to set before the edges burn. For thinner bakes, the standard temperature is usually fine.
• Filling depth — most batters fill the pan to 2/3 full. If your scaled batter would overflow, switch to a larger pan or use two pans.

Pitfall

Tube and Bundt pans are weird. A 10-inch Bundt holds ~12 cups of batter (the central hole displaces volume); a 9-inch round holds ~6 cups. Don't use the area cheat sheet for these — measure the pan with water if you're unsure.