Calculator Inputs
Adjust chain length, unsaturation, and ATP assumptions.
Example Data Table
These examples use common textbook ATP assumptions.
| Fatty Acid | Notation | Cycles | Acetyl-CoA | Propionyl-CoA | Net ATP |
|---|---|---|---|---|---|
| Palmitate | 16:0 | 7 | 8 | 0 | 106.00 |
| Stearate | 18:0 | 8 | 9 | 0 | 120.00 |
| Oleate | 18:1 | 8 | 9 | 0 | 118.50 |
| Linoleate | 18:2 | 8 | 9 | 0 | 114.50 |
| Heptadecanoate | 17:0 | 7 | 7 | 1 | 101.00 |
Formula Used
1) Chain classification
Even chains end with acetyl-CoA units only. Odd chains leave one propionyl-CoA unit.
2) Beta oxidation cycles
Even chain cycles = (n / 2) - 1
Odd chain cycles = (n - 3) / 2
3) Product counts
Even chains: acetyl-CoA = n / 2
Odd chains: acetyl-CoA = (n - 3) / 2, propionyl-CoA = 1
NADH = cycles
FADH2 = cycles - lost FADH2 from double bonds
4) Unsaturation adjustment
Each double bond removes one FADH2-forming step. Additional double bonds may also consume one reductive equivalent each.
5) ATP estimate
Net ATP = ATP from acetyl-CoA + ATP from propionyl-CoA + ATP from NADH + ATP from FADH2 - NADPH penalty - activation cost
Common default assumptions
NADH = 2.5 ATP, FADH2 = 1.5 ATP, acetyl-CoA = 10 ATP, propionyl-CoA pathway = 5 ATP, activation cost = 2 ATP.
How to Use This Calculator
- Enter the total number of carbon atoms.
- Enter the number of double bonds in the fatty acid.
- Keep the default ATP yields or enter your preferred assumptions.
- Enable the polyunsaturated penalty when modeling additional double-bond processing.
- Click the calculate button to generate the result.
- Review the ATP summary, product counts, and contribution chart.
- Export the result table or example table as CSV or PDF.
Notes and Assumptions
- This tool models standard mitochondrial beta oxidation.
- Very-long-chain handling before mitochondria is not included.
- Branched fatty acids are not included.
- Double-bond handling is simplified for practical estimation.
- ATP yields can vary across textbooks and research settings.
Frequently Asked Questions
1) What does this calculator estimate?
It estimates beta oxidation cycles, acetyl-CoA production, reducing equivalents, and net ATP yield for fatty acids using your selected biochemical assumptions.
2) Why do unsaturated fatty acids produce less ATP?
Double bonds bypass one FADH2-generating dehydrogenation step. Polyunsaturated chains may also require extra reducing power, which lowers the final ATP estimate further.
3) How are odd-chain fatty acids handled?
Odd chains finish with one propionyl-CoA instead of a final acetyl-CoA pair. This calculator adds a separate ATP contribution for that propionyl-CoA pathway.
4) Why is there an activation cost?
Fatty acids are first activated to acyl-CoA before beta oxidation begins. That initial step commonly costs the equivalent of 2 ATP.
5) Can I change textbook ATP assumptions?
Yes. You can edit ATP values for NADH, FADH2, acetyl-CoA, propionyl-CoA, activation cost, and the extra unsaturation penalty.
6) Does this tool model branched fatty acids?
No. Branched chains follow additional reactions and special cofactors. This page focuses on straight-chain beta oxidation estimates.
7) What chart is shown after calculation?
The chart displays ATP contributions from acetyl-CoA, propionyl-CoA, NADH, and FADH2, plus negative effects from activation and any extra penalty.
8) Can I export the results?
Yes. You can download the current calculation table or the example data table as CSV or PDF directly from the page.