Chemical Oxygen Demand Calculator

A Chemical Oxygen Demand calculator helps you find COD in water or wastewater. COD shows how much oxygen is needed to break down oxidizable matter.

This value is useful in water testing and wastewater work. You don't need to do the math by hand. We developed this calculator so users can easily calculate Chemical Oxygen Demand from lab test data.

The result is shown in mg O₂/L. A higher COD value means more oxidizable matter is present.

Chemical Oxygen Demand Formula

The core COD formula is:

COD = ((A − B) × N × 8000) / V

If the sample was diluted, use:

Final COD = ((A − B) × N × 8000 / V) × DF

Here:

• A = Blank titration volume in mL
• B = Sample titration volume in mL
• N = FAS normality
• V = Sample volume in mL
• DF = Dilution factor

The 8000 value converts the result to mg O₂/L.

Think of the blank as the starting point. The sample uses some of that titrant. The gap between them helps find the oxygen demand.

How to Use Online Chemical Oxygen Demand Calculator

1. Enter the blank volume
2. Enter the FAS volume used for the blank test. Use the value in mL.
3. Enter the sample volume
4. Enter the FAS volume used for your sample test. The blank value should normally be higher.
5. Enter FAS normality
6. Enter the standard FAS normality. For example, you may enter 0.1000 N.
7. Enter sample volume
8. Enter the water or wastewater sample volume used in the test.
9. Enter the dilution factor
10. Enter 1 if you didn't dilute the sample. Then click calculate. The tool will show the final COD in mg O₂/L.

Example Chemical Oxygen Demand Calculation

Let's use simple lab values.

Blank volume = 25 mL

Sample volume = 15 mL

FAS normality = 0.1000 N

Sample test volume = 10 mL

Dilution factor = 1

First, find the titration gap:

25 − 15 = 10 mL

Now use the COD formula:

COD = (10 × 0.1000 × 8000) / 10

COD = 800 mg O₂/L

Now apply the dilution factor:

800 × 1 = 800 mg O₂/L

So, the final Chemical Oxygen Demand is 800 mg O₂/L.

If the dilution factor were 5, the final value would be:

800 × 5 = 4000 mg O₂/L

Final Verdict

A Chemical Oxygen Demand calculator makes COD testing math quick and simple. Just enter your blank value, sample value, FAS normality, sample volume, and dilution factor.

The tool then applies the COD formula and gives the result in mg O₂/L. It's a handy choice for water quality checks, wastewater analysis, and lab work.

FAQs

What is Chemical Oxygen Demand?

Chemical Oxygen Demand, or COD, measures the oxygen needed to oxidize matter in a water sample.

What is the COD unit?

COD is usually reported as mg O₂/L.

What does a high COD mean?

A high COD often means the water has more oxidizable matter.

Why is 8000 used in the COD formula?

The 8000 factor converts the titration result into the oxygen demand unit, mg O₂/L.

What if my sample was diluted?

Multiply the measured COD by the dilution factor to get the original sample value.