For fixation of six CO2 molecules during Calvin cycle of photosynthesis, 18 molecules of ATP and 12 molecules of NADPH2 are required.
One molecule of glyceraldehyde-3-phosphate. (3-carbon molecules) is formed by fixation of 3CO2 molecules. So 9 ATP and 6 NADPH molecules are required for formation of glyceraldehyde phesphate. 3CO2+6NADPH+9ATP⟶ Glyceraldehyde-3 phosphatge +6NADP++9ADP+8Pi