Chemical Oxygen Demand (COD) Calculator

Calculate the oxygen demand of your water or wastewater sample using titration data.

Enter your titration results and sample details to determine the COD value in mg/L or g/L. This tool supports standard laboratory methods and provides step-by-step explanations.

COD Calculation Examples

See how to calculate Chemical Oxygen Demand with real-world data.

Standard Laboratory COD Test

Standard

A typical COD test for a wastewater sample using 12.5 mL titrant, 1.2 mL blank, 0.025 N titrant, and 50 mL sample volume.

Titrant Volume (A): 12.5 mL

Blank Volume (B): 1.2 mL

Titrant Normality (N): 0.025 mol/L

Sample Volume (V): 50 mL

Result Unit: mg/L

Low COD in Drinking Water

Low Concentration

A drinking water sample with very low organic content: 0.8 mL titrant, 0.1 mL blank, 0.01 N titrant, 100 mL sample volume.

Titrant Volume (A): 0.8 mL

Blank Volume (B): 0.1 mL

Titrant Normality (N): 0.01 mol/L

Sample Volume (V): 100 mL

Result Unit: mg/L

Industrial Wastewater High COD

High Concentration

Industrial effluent with high organic load: 30 mL titrant, 2.5 mL blank, 0.1 N titrant, 25 mL sample volume.

Titrant Volume (A): 30 mL

Blank Volume (B): 2.5 mL

Titrant Normality (N): 0.1 mol/L

Sample Volume (V): 25 mL

Result Unit: mg/L

COD in g/L for Research

g/L Unit

A research sample where result is needed in g/L: 15 mL titrant, 1.5 mL blank, 0.05 N titrant, 100 mL sample volume, result in g/L.

Titrant Volume (A): 15 mL

Blank Volume (B): 1.5 mL

Titrant Normality (N): 0.05 mol/L

Sample Volume (V): 100 mL

Result Unit: g/L

Other Titles
Understanding Chemical Oxygen Demand (COD): A Comprehensive Guide
Everything you need to know about COD, its calculation, and real-world significance.

What is Chemical Oxygen Demand (COD)?

  • Definition and Importance
  • Relation to Water Quality
  • Comparison with BOD
Chemical Oxygen Demand (COD) is a critical parameter in water and wastewater analysis, representing the amount of oxygen required to chemically oxidize organic compounds present in a sample. It is widely used to assess the level of organic pollution in water bodies and is a key indicator in environmental monitoring and wastewater treatment.
Why is COD Important?
COD provides a rapid and reliable measure of water quality, helping to identify pollution sources and evaluate treatment efficiency. Unlike Biological Oxygen Demand (BOD), COD does not rely on biological processes and can be determined in a few hours.

COD in Practice

  • Measuring COD in river water to assess pollution.
  • Comparing COD and BOD values in wastewater treatment.

Step-by-Step Guide to Using the COD Calculator

  • Input Data Collection
  • Calculation Process
  • Result Interpretation
How to Use the Calculator
  1. Enter the titrant volume (A) used for your sample.
  2. Enter the blank titrant volume (B).
  3. Specify the normality (N) of your titrant.
  4. Enter the sample volume (V).
  5. Select the desired result unit (mg/L or g/L).
  6. Click 'Calculate COD' to get your result.
The calculator will display the COD value and the calculation steps for full transparency.

Step-by-Step Examples

  • A laboratory technician enters titration data to calculate COD.
  • A student uses the tool for a chemistry assignment.

Real-World Applications of COD

  • Environmental Monitoring
  • Industrial Wastewater Treatment
  • Research and Education
Where is COD Used?
COD is essential in monitoring rivers, lakes, and industrial effluents. It helps regulatory agencies enforce pollution limits and industries optimize treatment processes.
Researchers and educators use COD data to study organic matter dynamics and teach water chemistry concepts.

Applications in Action

  • Environmental agency monitors COD in a river.
  • Factory adjusts treatment process based on COD results.

Common Misconceptions and Correct Methods

  • Misunderstanding Blank Correction
  • Unit Conversion Errors
  • Sample Handling Issues
Avoiding Calculation Mistakes
Always subtract the sample titrant volume from the blank to avoid negative COD values. Ensure all volumes are in the correct units and the titrant normality is accurate.
Proper sample handling and timely analysis are crucial for reliable results.

Common Pitfalls

  • Incorrectly using sample volume instead of blank volume.
  • Forgetting to convert mg/L to g/L.

Mathematical Derivation and Examples

  • COD Formula Explained
  • Worked Example Calculations
  • Unit Conversions
The COD Calculation Formula
COD (mg/L) = ((B - A) × N × 8000) / V, where B is blank titrant volume (mL), A is sample titrant volume (mL), N is titrant normality (mol/L), and V is sample volume (mL). The factor 8000 accounts for oxygen's equivalent weight and unit conversions.
To convert mg/L to g/L, simply divide by 1000.

Mathematical Examples

  • Sample: A=12.5, B=1.2, N=0.025, V=50 → COD=44.8 mg/L.
  • Sample: A=15, B=1.5, N=0.05, V=100 → COD=5.4 mg/L or 0.0054 g/L.