OD600 reading (absorbance)

Organism preset

Conversion factor (CFU/mL at OD 1.0)

Sample dilution before reading (1 = undiluted)

Culture volume (mL, optional → total cells)

—

estimated CFU/mL

⚠ OD above ~0.8 is outside the linear range of most spectrophotometers. Dilute the culture, re-read, and enter the dilution above for a more reliable estimate.

ℹ OD below ~0.1 gives noisy readings. Treat this estimate as rough.