Electron Transport Chain Calculator

The Electron Transport Chain (ETC) is the final stage of cellular respiration where electrons from energy carriers are used to produce ATP — the cell's primary energy currency. Enter the number of NADH and FADH2 molecules, select your ATP yield per carrier, and optionally include substrate-level phosphorylation to calculate Total ATP Produced. Secondary outputs include ATP from NADH, ATP from FADH2, total electrons transferred, and energy conversion efficiency. Also try the Fermentation Calculator.

molecules

Each NADH typically produces 2.5 ATP

molecules

Each FADH2 typically produces 1.5 ATP

Add ATP from glycolysis and citric acid cycle

ATP

Typical: 2 from glycolysis + 2 from citric acid cycle

Results

Total ATP Produced

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ATP from NADH

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ATP from FADH2

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Total Electrons Transferred

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Energy Conversion Efficiency

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Frequently Asked Questions

How does the electron transport chain produce ATP?

The electron transport chain uses energy from electron transfers to pump protons across the inner mitochondrial membrane, creating a gradient that drives ATP synthase to produce ATP through chemiosmosis. See also our Krebs Cycle Calculator.

Why does NADH produce more ATP than FADH2?

NADH enters the electron transport chain at Complex I, while FADH2 enters at Complex II. NADH passes through more proton-pumping complexes, generating more ATP per molecule.

What is the theoretical vs actual ATP yield?

Theoretical maximum is 3 ATP per NADH and 2 per FADH2, but actual yields are typically 2.5 and 1.5 respectively due to energy costs of transport and other cellular processes. You might also find our ATP Yield Calculator useful.

Where do NADH and FADH2 come from in cellular respiration?

NADH is produced in glycolysis, pyruvate oxidation, and the citric acid cycle. FADH2 is primarily produced in the citric acid cycle and fatty acid oxidation.

What happens if oxygen is not available?

Without oxygen as the final electron acceptor, the electron transport chain stops functioning, and cells must rely on anaerobic processes like fermentation for ATP production.

How many protons are pumped per electron pair?

Complex I pumps 4 protons, Complex III pumps 4 protons, and Complex IV pumps 2 protons per electron pair, totaling 10 protons for NADH oxidation.