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Baking pan size conversion calculator

Two tins are interchangeable when their volumes match. The calculator compares areas and volumes and tells you how the batter depth changes.

cm
cm
cm
cm
cm
Batter depth in the new tin
2.38cm
≈ Rounded Baking pan conversion
Area ratio Multiply the recipe by this to keep the same depth.
1.6839
Original tin area
314.2 cm2
New tin area
529.0 cm2
Batter volume
1.257 L
Recipe multiplier for the same depth
1.6839
Show the working
  1. Original tin shape = 1
  2. Original diameter or length = 20
  3. Original width (rectangular only) = 20
  4. New tin shape = 0
  5. New diameter or length = 23
  6. New width (rectangular only) = 23
  7. Batter depth in the original = 4
  8. Original tin area = 1 > 0 ? pi * (20/2)^2 : 20 * 20 = 314.159
  9. New tin area = 0 > 0 ? pi * (23/2)^2 : 23 * 23 = 529
  10. Area ratio = 314.159 > 0 ? 529 / 314.159 : 0 = 1.683 86
  11. volume = 314.159 * 4 = 1256.64
  12. Batter depth in the new tin = 529 > 0 ? 1256.64 / 529 : 0 = 2.3755
  13. Recipe multiplier for the same depth = 1.683 86 = 1.683 86
  14. Batter volume = 1256.64 / 1000 = 1.256 64

Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.

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    The formula

    • round tin area = pi (diameter/2)^2
    • rectangular tin area = length x width
    • new depth = original area x original depth / new area

    A batter deeper than about 5 cm needs a lower oven and a longer bake, or the outside sets before the middle rises.

    A 20 cm round tin and a 20 cm square tin are not interchangeable: the square holds 27% more.

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