Free Chemical Oxygen Demand Calculator
Use this Free Chemical Oxygen Demand Calculator to work through the same calculation as the main calculator page with clear steps, examples, and result context.
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Run the calculator.
What This Free Chemical Oxygen Demand Calculator Helps You Do
This page helps you convert standard COD titration readings into an mg/L result using the exact relationship highlighted in the Omni reference. It is built for quick lab calculations and wastewater-screening checks.
The output also places the COD value into practical context by comparing it with the low range commonly cited for drinking water, while still reminding you that COD alone is not a complete safety assessment.
How to Calculate Free Chemical Oxygen Demand Calculator
- Enter blank and sample FAS volumes: Use the titration readings for the blank and the sample.
- Enter FAS normality: Use the normality that belongs to the titrant used in the COD procedure.
- Enter sample volume: Volumes should stay in milliliters for the standard mg/L result.
- Interpret COD: Higher COD indicates more oxidizable material in the water sample.
Free Chemical Oxygen Demand Calculator Formula
| Variable | Meaning | Unit |
|---|---|---|
| COD | Chemical oxygen demand | mg/L |
| A | FAS volume for the blank run | mL |
| B | FAS volume for the sample | mL |
| N | Normality of FAS | N |
| Sample volume | Original sample volume | mL |
Use the worked examples below to check how the formula behaves with real values. If the result looks unexpected, verify the unit assumptions and the meaning of each variable before interpreting the answer.
Worked Examples
- A: 12.4 mL
- B: 5.8 mL
- N: 0.1
- Sample: 50 mL
Result: COD is 105.6 mg/L.
The sample contains a moderate oxidizable load relative to clean drinking water.
- A: 10 mL
- B: 9.4 mL
- N: 0.1
- Sample: 50 mL
Result: COD is 9.6 mg/L.
This lands near the lower end of the preferred drinking-water range mentioned by Omni.
- A: 18 mL
- B: 4 mL
- N: 0.25
- Sample: 25 mL
Result: COD is 1120 mg/L.
This indicates a heavily contaminated sample with high oxygen demand.
- A: 15.2 mL
- B: 10.6 mL
- N: 0.2
- Sample: 100 mL
Result: COD is 73.6 mg/L.
This is above drinking-water guidance and suggests the water needs treatment assessment.
How to Interpret Your Results
| Range | Meaning | Action |
|---|---|---|
| Around 10 to 20 mg/L | This aligns with the preferred COD range often cited for drinking water. | Remember that COD alone does not prove the water is safe. |
| Moderate COD | Organic or oxidizable load is present. | Compare against site limits or treatment targets rather than using COD in isolation. |
| High COD | The sample contains substantial oxidizable contaminants. | Investigate pollutant sources and review treatment performance. |
Frequently Asked Questions
References
Last reviewed: March 2026