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Calcimator

Cell Doubling Time

Calculate cell doubling time, growth rate, and generation count from optical density measurements over time.

Inputs

Results

Doubling Time

1.33 hrs

Growth Rate Constant (k)

0.5199 hr⁻¹

Number of Generations

3

Growth Ratio (Nf/Ni)8
Specific Growth Rate (μ)0.5199 hr⁻¹
How to Use This Calculator
  1. Enter Initial OD (Optical Density), Final OD (Optical Density), and Elapsed Time (hours).
  2. Review Doubling Time (hrs), Growth Rate Constant (k) (hr⁻¹), and Number of Generations.
  3. Use Growth Ratio (Nf/Ni) and Specific Growth Rate (μ) (hr⁻¹) to inform your decision.
  4. Use the chart to visualize the results and explore different scenarios by adjusting inputs.

How the result changes with Elapsed Time (hours)

Elapsed Time (hours)Doubling TimeGrowth Rate Constant (k)Number of Generations
10033.33 hrs0.0208 hr⁻¹3
350116.67 hrs0.0059 hr⁻¹3
650216.67 hrs0.0032 hr⁻¹3
900300 hrs0.0023 hr⁻¹3

What each input means

Initial OD (Optical Density)
Optical density at the start of exponential growth phase (OD₆₀₀ for bacteria).
Final OD (Optical Density)
Optical density at the end of the measurement period. Must be greater than initial OD.
Elapsed Time (hours)
Time elapsed between initial and final OD measurements in hours.

How this is calculated

Formula

tᵈ = t × ln(2) / ln(Nᶠ / Nᵢ)

Worked example, using the default values

  1. Identify Input Parameters
    Initial OD (Optical Density) = 0.1, Final OD (Optical Density) = 0.8, Elapsed Time (hours) = 4 = 3 input(s) provided
  2. Calculate Doubling Time
    Doubling Time
    1.33 = 1.33
  3. Calculate Growth Rate Constant
    Growth Rate Constant
    0.5199 = 0.5199
  4. Calculate Number of Generations
    Number of Generations
    3 = 3
  5. Calculate Growth Ratio
    Growth Ratio
    8 = 8
  6. Calculate Specific Growth Rate
    Specific Growth Rate
    0.5199 = 0.5199

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