💧 Biological Oxygen Demand (BOD) Calculator
Calculate the 5-day Biological Oxygen Demand (BOD5) of a water sample from dissolved oxygen readings, a key indicator of organic pollution in water quality testing.
What is Biological Oxygen Demand?
Biological Oxygen Demand (BOD) measures how much dissolved oxygen microorganisms consume while breaking down organic matter in a water sample over a set incubation period, usually 5 days (BOD5). Higher BOD generally indicates more organic pollution and less oxygen available for aquatic life.
How this calculator works
The standard BOD5 test compares dissolved oxygen (DO) in a diluted sample immediately after preparation (Day 0) to DO after 5 days of dark incubation at 20°C (Day 5). The calculator uses the standard formula:
- BOD5 = (D1 – D2) / P
- D1 = initial dissolved oxygen (mg/L)
- D2 = dissolved oxygen after 5 days (mg/L)
- P = decimal fraction of the bottle volume that is sample (dilution factor)
Enter your Day 0 and Day 5 DO readings and the percentage of the bottle that was actual sample (the rest being dilution water). This tool is intended for general water-quality education and field-monitoring reference. Laboratory testing following standard methods (such as APHA Standard Methods) should be used for regulatory or official reporting.