OD Cfu Calibration Interpolation

Interpolate CFU from an organism- and instrument-specific blank-corrected OD calibration, then undo dilution without out-of-range extrapolation.

Description

Optical density does not universally convert to CFU.

Optical density does not universally convert to CFU. An organism- and instrument-specific calibration can support in-range interpolation after blank correction, followed by undoing the sample's dilution.^[1]

Interpolate CFU from an organism- and instrument-specific blank-corrected OD calibration, then undo dilution without out-of-range extrapolation.

When to use OD Cfu Calibration Interpolation

Use this tool to interpolate CFU from an organism- and instrument-specific blank-corrected OD calibration, then undo dilution without out-of-range extrapolation.

Prepare the sample, count, growth or assay measurements requested by this tool. Confirm units, sampling periods and reporting bases; supply independently established comparison criteria where requested.

How to use OD Cfu Calibration Interpolation and understand its results

Prepare the sample, count, growth or assay measurements requested by this tool. Confirm units, sampling periods and reporting bases; supply independently established comparison criteria where requested.
Enter sampleOd, blankOd, calibrationCorrectedOds, calibrationCfuPerMl, dilutionFactor using the field table and calculation rules, then run the tool.
Read correctedSampleOd, interpolatedCfuPerMl, undilutedCfuPerMl. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
sampleOd	Sample od	number; minimum: 0	Required
blankOd	Blank od	number; minimum: 0	Required
calibrationCorrectedOds	Calibration corrected ods	list of number	Required
calibrationCfuPerMl	Calibration cfu per ml	list of number	Required
dilutionFactor	Dilution factor	number	Required

Enter at least two aligned nonnegative calibration OD/CFU values with strictly increasing ODs, nonnegative sample/blank ODs and dilution factor at least one. The corrected OD must lie in the calibration range apart from a 10⁻¹² boundary tolerance, within which it is clamped for interpolation. Return corrected OD, interpolated CFU/mL and dilution-adjusted CFU/mL.

Paired lists must be nonempty and have equal lengths. Sequences checked for increasing order must be nonempty and strictly increasing; additional calculation rules may require more samples.

correctedOD=max(0,sampleOD−blankOD); undilutedCFU=linearInterpolation(correctedOD) × dilutionFactor

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
correctedSampleOd	Corrected sample od	number
interpolatedCfuPerMl	Interpolated cfu per ml	number
undilutedCfuPerMl	Undiluted cfu per ml	number

json

{
  "input": {
    "sampleOd": 0.3,
    "blankOd": 0.1,
    "calibrationCorrectedOds": [
      0.1,
      0.3
    ],
    "calibrationCfuPerMl": [
      1000000,
      3000000
    ],
    "dilutionFactor": 2
  },
  "output": {
    "correctedSampleOd": 0.19999999999999998,
    "interpolatedCfuPerMl": 1999999.9999999998,
    "undilutedCfuPerMl": 3999999.9999999995
  }
}

Limitations and assumptions

No out-of-range extrapolation, universal calibration or uncertainty is inferred. Blank correction clips negative differences to zero; calibration CFUs need not be monotone, so their physical suitability remains the caller's responsibility.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Stationary Phase Window Audit: Screen the final growth-curve window for a caller-defined relative stability band, rather than equating one count with carrying capacity. For a complementary task, use Countable Plate Selection: Select colony-count plates within caller-specified countability limits, retaining low and excessive counts separately.

References

OD Cfu Calibration Interpolation — tool.io

Similar or alternative tools

Stationary Phase Window Audit
Screen the final growth-curve window for a caller-defined relative stability band, rather than equating one count with carrying capacity.
Countable Plate Selection
Select colony-count plates within caller-specified countability limits, retaining low and excessive counts separately.