The exact factor
One inch is exactly 2.54 cm by definition. A 9-inch cake tin is 22.86 cm — sold as a 23 cm tin in Europe, which is close enough for baking.
Common pan sizes
- 6 in = 15 cm · 7 in = 18 cm · 8 in = 20 cm
- 9 in = 23 cm · 10 in = 25 cm
- 9 × 13 in = 23 × 33 cm (the standard sheet pan)
- 8 in springform = 20 cm, the most common cheesecake size
Where a centimetre matters
Pan sizing is nominal: a "20 cm" tin may measure 20.5 cm. For layered cakes, a 1 cm difference changes the batter depth by about 10% — enough to adjust the bake time.
Rolling and pastry
Pastry thickness is often given in inches (1/8 in = 3 mm). A ruler is more reliable than guessing, and 3 mm is the standard for tart cases.
Frequently Asked Questions
What is a 9-inch pan in cm?
22.86 cm — sold as 23 cm in metric countries.
Is a 20 cm tin the same as 8 inches?
Nearly: 8 in = 20.32 cm, so a 20 cm tin is marginally smaller.
How thick should pastry be?
About 3 mm (1/8 inch) for tarts, 5 mm for pie bases.
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