Optical density at 600 nm to cells per milliliter
Type a value in OD600 to get it in cells/mL instantly.
That's 2× as dense as a culture in mid-log phase, while a culture in stationary phase is 2.5× denser. A 10 mL culture at that density holds about 8×10⁹ cells.
Convert the other way: cells/mL to OD600
What it means
How dense is that culture?
Conversion factors are rules of thumb for a 1 cm path length. They differ between spectrophotometers, strains and growth phases, so calibrate your own.
The math
How to convert OD600 to cells/mL
Optical density is a proxy, scaled by the organism: cells/mL = OD600 × cells per mL at OD 1. The figures below use the organism selected above.
Example: 1 OD600 = 800,000,000 cells/mL.
The table below is for E. coli (8 × 10⁸ per mL at OD 1).
Every unit
Your density in every unit
Tables
OD600 to cells/mL conversion table
| OD600 | cells/mL |
|---|---|
| 10,000 OD600 | 8×10¹² cells/mL |
| 100,000 OD600 | 8×10¹³ cells/mL |
| 1,000,000 OD600 | 8×10¹⁴ cells/mL |
| 5,000,000 OD600 | 4×10¹⁵ cells/mL |
| 10,000,000 OD600 | 8×10¹⁵ cells/mL |
| 50,000,000 OD600 | 4×10¹⁶ cells/mL |
| 100,000,000 OD600 | 8×10¹⁶ cells/mL |
| 500,000,000 OD600 | 4×10¹⁷ cells/mL |
| 1×10⁹ OD600 | 8×10¹⁷ cells/mL |
cells/mL to OD600 conversion table
| cells/mL | OD600 |
|---|---|
| 10,000 cells/mL | 1.25×10⁻⁵ OD600 |
| 100,000 cells/mL | 0.000125 OD600 |
| 1,000,000 cells/mL | 0.00125 OD600 |
| 5,000,000 cells/mL | 0.00625 OD600 |
| 10,000,000 cells/mL | 0.0125 OD600 |
| 50,000,000 cells/mL | 0.0625 OD600 |
| 100,000,000 cells/mL | 0.125 OD600 |
| 500,000,000 cells/mL | 0.625 OD600 |
| 1×10⁹ cells/mL | 1.25 OD600 |
Quick answers
Quick answers
- How many cells/mL is 1 OD600?
- 1 OD600 is 800,000,000 cells/mL.
- How many cells/mL is 10 OD600?
- 10 OD600 is 8×10⁹ cells/mL.
The units
About these units
Optical density at 600 nm (OD600)
What the spectrophotometer reads. A proxy for cell number, not a count.
Cells per milliliter (cells/mL)
The real count, as a hemocytometer or counter reports it.
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