Chemical Oxygen Demand (COD

Chemical Oxygen Demand (COD) measures the amount of oxygen required to chemically oxidize organic and inorganic pollutants in water using potassium dichromate.

To use the Chemical Oxygen Demand (COD) Calculator, enter your Normality of FAS Titrant (N), Volume of FAS for Blank (Vb), Volume of FAS for Sample (Vs) and other values. The calculator instantly computes Chemical Oxygen Demand (COD), Wastewater Assessment Status. Results update in real time as you change any input — no submit button needed.

How to Use This Calculator

Enter your Normality of FAS Titrant (N) (e.g. 0.10), Volume of FAS for Blank (Vb) (e.g. 25.0 in mL), Volume of FAS for Sample (Vs) (e.g. 14.5 in mL), and Volume of Water Sample Analyzed (e.g. 50.0 in mL). Results update instantly as you type — no submit button or page reload required. Adjust any value to compare scenarios side by side.

The Formula

COD (mg/L O₂) = [(Vb - Vs) × N × 8000] ÷ Sample Volume (mL)

Where Vb = Volume of FAS for blank (mL), Vs = Volume of FAS for sample (mL), N = Normality of FAS, 8000 = milliequivalent weight of oxygen (8 × 1000).

Worked Example

Testing industrial wastewater sample (50 mL) using 0.10 N FAS titrant.

• Blank Titration Volume Vb = 25.0 mL.

• Sample Titration Volume Vs = 14.5 mL.

• COD = [(25.0 - 14.5) × 0.10 × 8000] ÷ 50.0 = 168.00 mg/L O₂ (Domestic wastewater range).

Understanding Your Result

Evaluate your result against the specific financial decision driving this calculation. Small input differences can create large output swings — run two or three scenarios (conservative, base, optimistic) to understand the range of outcomes. For decisions involving more than a month's income, validate your result against a second source or consult a certified financial planner (CFP) or CPA depending on the tax implications.