In terms of the area of the 2 pans, the 9" is 27% greater than the 8" pan.
If you are scaling your ingredients you can multiply by 1.27 and that should do it. If you are using the scoop and level method, the nearest approximation would be 1/4 extra of everything (a cup of flour would become 1 1/4 cups, a tsp of salt would become 1 1/4 tsp, etc.)
You would need to adjust the baking time because there is more batter to cook. I don't know if there is a formula for that. Keep a close eye on it after the stated time in the original recipe until you can determine the new baking time for future efforts.
Jock
If you are scaling your ingredients you can multiply by 1.27 and that should do it. If you are using the scoop and level method, the nearest approximation would be 1/4 extra of everything (a cup of flour would become 1 1/4 cups, a tsp of salt would become 1 1/4 tsp, etc.)
You would need to adjust the baking time because there is more batter to cook. I don't know if there is a formula for that. Keep a close eye on it after the stated time in the original recipe until you can determine the new baking time for future efforts.
Jock
