Recipe made for one pan but you have another? Get the exact factor to multiply your recipe by (based on pan area, same depth).
Cakes scale by pan area (assuming the same batter depth). Round area = π·r². Square/rect area = L·W. Factor = your pan area ÷ original pan area. If your pan is deeper, you can fill a bit more; watch bake time — bigger/thinner bakes faster, smaller/deeper slower.