The immediate net carbohydrate product of the Calvin cycle is a three-carbon triose phosphate, commonly represented as glyceraldehyde-3-phosphate (G3P), rather than a glucose molecule appearing directly from one cycle turn.

Three $CO_2$ molecules produce one net three-carbon G3P equivalent. Therefore two net G3P molecules contain enough fixed carbon to form one six-carbon hexose—a six-carbon sugar—equivalent:

$$2\times3\ \mathrm{C}=6\ \mathrm{C}.$$

Using standard Calvin-cycle resource bookkeeping, obtaining that much net fixed carbon requires fixation of

$$6\ CO_2$$

and use of

$$18\ ATP+12\ NADPH$$

before downstream carbohydrate-synthesis costs are included.

Fixed carbon can follow several routes

Triose phosphates are branch-point metabolites rather than dedicated glucose molecules.

They can be rearranged into hexose phosphates used to make soluble sugars and storage carbohydrates, or their carbon skeletons can enter other biosynthetic pathways.

Thus the phrase “photosynthesis makes glucose” is a useful overall simplification but not a literal description of the Calvin cycle's immediate output.

Light reactions and carbon fixation exchange recyclable carriers

The two major photosynthetic subsystems are coupled by ATP and NADPH:

light-driven reactions
ADP + Pi + NADP+ → ATP + NADPH

                     ↓
                 Calvin cycle
                     ↓
CO2 → triose phosphate

carrier forms returned:
ATP → ADP + Pi
NADPH → NADP+

ATP and NADPH are not incorporated wholesale into carbohydrate. ATP is consumed through coupled chemical reactions, while NADPH transfers reducing equivalents and is oxidized back to NADP$^+$.

This closes the photosynthetic carrier cycle: light-driven electron transfer continually replenishes ATP and NADPH, while carbon-fixation chemistry consumes those forms to convert $CO_2$ into reduced organic carbon.