Serial Dilution & Colony Count Calculator

Starting CFU/mL 1.0 × 10⁶

10³10⁹

Dilution factor 10×

2×100×

Volume plated (mL) 0.1

0.011.0
10⁶CFU/mL
÷
10dilution
×
0.1mL
=
~100colonies

Calculated Original Concentration (from best plate)

1.0 × 10⁶ CFU/mL
Tip: A countable plate has 30–300 colonies. If all plates are too crowded or too sparse, adjust the dilution factor or starting concentration.