How much ATP does Krebs cycle produce?

Each turn of the Krebs cycle produces 1 molecule of GTP (or ATP) through substrate-level phosphorylation. Additionally, it generates 3 NADH and 1 FADH₂, which, via oxidative phosphorylation, yield about 9 ATP equivalents. Together with the direct GTP (or ATP), the total energy output per cycle turn is about 10 ATP equivalents. Since one glucose yields two turns of the Krebs cycle, the total energy contribution from the Krebs cycle per glucose molecule is approximately 20 ATP equivalents.