Yield% = $\frac{actual yield}{theoretical yield}$ x 100. Theoretical yield = maximum from stoichiometry. If yield = 80%, actual = 0.8 x theoretical. For sequential reactions: A -> B -> C. If step 1 has 80% yield and step 2 has 75% yield, overall yield = 0.8 x 0.75 = 0.6 = 60%. Track moles through each step, applying yield as a multiplier. Example: 100 g A (M=50) -> B -> C. Moles A = 2. If A:B = 1:1 and B:C = 1:1, theoretical C = 2 mol. With 80% and 75%: actual C = 2 x 0.8 x 0.75 = 1.2 mol.