Six oxygen molecules are released when one glucose molecule is formed in the standard overall equation for oxygenic photosynthesis. The balanced summary is 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.
This equation means that six carbon dioxide molecules and six water molecules provide the atoms rearranged into one glucose molecule and six molecules of oxygen. The glucose represents stored chemical energy and carbon skeletons that plants can use to make starch, cellulose, sucrose, and many other compounds.
A common misconception is that the released oxygen comes from carbon dioxide. In the light-dependent reactions, Photosystem II splits water in the thylakoid membrane; oxygen atoms from water combine to form O₂, which diffuses away as a by-product. The equation is an overall bookkeeping model, not a single reaction. Photosynthesis proceeds through light reactions and the Calvin cycle, and the glucose label summarizes products made after carbon fixation rather than a molecule assembled in one step.