Cell culture

OD600 / cell density: practice problems

Convert the OD reading, or work out the back-dilution. Every answer here is computed by the same tested calculator the rest of the site uses, so a solution can never drift away from the maths.

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Problem 1 OD600 / cell density

Convert the OD reading, or work out the back-dilution.

  • OD600 (measured): 0.6
  • Cells/mL per OD: 8e8
Show the answer and the working

That culture is about 4.8 × 10⁸ cells/mL.

  1. Multiply OD by the strain factor: cells/mL = OD600 · factor
  2. Substitute: cells/mL = 0.6 · 800000000 = 480000000 cells/mL

Open this in the calculator to change the numbers.

Problem 2 OD600 / cell density

Convert the OD reading, or work out the back-dilution.

  • Mode: Dilute to target OD
  • Current OD (dilute mode): 5
  • Target OD (dilute mode): 0.1
  • Final volume (dilute mode): 9 mL
Show the answer and the working

Mix 0.18 mL of culture with 8.82 mL of fresh medium.

  1. Solve for culture volume: V₁ = (OD₂ · V₂) / OD₁
  2. Substitute: V₁ = (0.1 · 9 mL) / 5 = 0.18 mL
  3. Fresh medium: V₂ − V₁ = 8.82 mL

Open this in the calculator to change the numbers.

Problem 3 OD600 / cell density

Convert the OD reading, or work out the back-dilution.

  • OD600 (measured): 0.75
  • Cells/mL per OD: 8e8
Show the answer and the working

That culture is about 6 × 10⁸ cells/mL.

  1. Multiply OD by the strain factor: cells/mL = OD600 · factor
  2. Substitute: cells/mL = 0.75 · 800000000 = 600000000 cells/mL

Open this in the calculator to change the numbers.

Problem 4 OD600 / cell density

Convert the OD reading, or work out the back-dilution.

  • Mode: Dilute to target OD
  • Current OD (dilute mode): 4
  • Target OD (dilute mode): 0.1
  • Final volume (dilute mode): 11 mL
Show the answer and the working

Mix 0.275 mL of culture with 10.73 mL of fresh medium.

  1. Solve for culture volume: V₁ = (OD₂ · V₂) / OD₁
  2. Substitute: V₁ = (0.1 · 11 mL) / 4 = 0.275 mL
  3. Fresh medium: V₂ − V₁ = 10.725 mL

Open this in the calculator to change the numbers.

Problem 5 OD600 / cell density

Convert the OD reading, or work out the back-dilution.

  • OD600 (measured): 0.4
  • Cells/mL per OD: 8e8
Show the answer and the working

That culture is about 3.2 × 10⁸ cells/mL.

  1. Multiply OD by the strain factor: cells/mL = OD600 · factor
  2. Substitute: cells/mL = 0.4 · 800000000 = 320000000 cells/mL

Open this in the calculator to change the numbers.

Problem 6 OD600 / cell density

Convert the OD reading, or work out the back-dilution.

  • Mode: Dilute to target OD
  • Current OD (dilute mode): 5
  • Target OD (dilute mode): 0.25
  • Final volume (dilute mode): 10 mL
Show the answer and the working

Mix 0.5 mL of culture with 9.5 mL of fresh medium.

  1. Solve for culture volume: V₁ = (OD₂ · V₂) / OD₁
  2. Substitute: V₁ = (0.25 · 10 mL) / 5 = 0.5 mL
  3. Fresh medium: V₂ − V₁ = 9.5 mL

Open this in the calculator to change the numbers.

Problem 7 OD600 / cell density

Convert the OD reading, or work out the back-dilution.

  • OD600 (measured): 0.15
  • Cells/mL per OD: 8e8
Show the answer and the working

That culture is about 1.2 × 10⁸ cells/mL.

  1. Multiply OD by the strain factor: cells/mL = OD600 · factor
  2. Substitute: cells/mL = 0.15 · 800000000 = 120000000 cells/mL

Open this in the calculator to change the numbers.

Problem 8 OD600 / cell density

Convert the OD reading, or work out the back-dilution.

  • Mode: Dilute to target OD
  • Current OD (dilute mode): 1
  • Target OD (dilute mode): 0.15
  • Final volume (dilute mode): 8 mL
Show the answer and the working

Mix 1.2 mL of culture with 6.8 mL of fresh medium.

  1. Solve for culture volume: V₁ = (OD₂ · V₂) / OD₁
  2. Substitute: V₁ = (0.15 · 8 mL) / 1 = 1.2 mL
  3. Fresh medium: V₂ − V₁ = 6.8 mL

Open this in the calculator to change the numbers.

Problem 9 OD600 / cell density

Convert the OD reading, or work out the back-dilution.

  • OD600 (measured): 0.1
  • Cells/mL per OD: 8e8
Show the answer and the working

That culture is about 8 × 10⁷ cells/mL.

  1. Multiply OD by the strain factor: cells/mL = OD600 · factor
  2. Substitute: cells/mL = 0.1 · 800000000 = 80000000 cells/mL

Open this in the calculator to change the numbers.

Problem 10 OD600 / cell density

Convert the OD reading, or work out the back-dilution.

  • Mode: Dilute to target OD
  • Current OD (dilute mode): 3
  • Target OD (dilute mode): 0.4
  • Final volume (dilute mode): 9 mL
Show the answer and the working

Mix 1.2 mL of culture with 7.8 mL of fresh medium.

  1. Solve for culture volume: V₁ = (OD₂ · V₂) / OD₁
  2. Substitute: V₁ = (0.4 · 9 mL) / 3 = 1.2 mL
  3. Fresh medium: V₂ − V₁ = 7.8 mL

Open this in the calculator to change the numbers.

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