Here's a rough guide for butter-based cakes that use the creaming method. If in doubt, simply fill the pan up to 1/2 - 2/3 full. If there is too much batter, you may have to use a 2nd pan.
Place the pan on a scale, reset the scale to zero, and pour in the batter.
4" round pan: 180g-250g of batter, Bake for around 25-35min @ 170 or 180 deg Celsius
6" round pan: 300g-500g of batter, Bake for around 30-45min @ 170 or 180 deg Celsius
8" round pan: 700g-1kg of batter, Bake for around 40-50min @ 170 or 180 deg Celsius
10" round pan: 1.5kg-2kg of batter. Divide into two 10" pans and bake each one for 35-45min @ 170 or 180 deg Celsius
** For an airy sponge cake recipe, fill the pan up to 1/2 - 2/3 full, disregarding the weight of the cake batter.
Disclaimer ;) Baking times and temperatures may vary by depending on the recipe and your oven, but this is what we have learned over the years =)