Understand the relationship
The reasoning behind the result
OD is being used as a proportional proxy
The dilution equation assumes optical density is proportional to the relevant concentration within the actual measurement range. It conserves that concentration–volume product rather than treating OD as a count of organisms.
Bacterial turbidity involves scattering and instrument-dependent response. The tool does not supply a universal linear range or convert OD into viable cells, CFU or biomass.
Two starting volumes, one conservation equation
Vstock = Vfinal ODtarget/ODstock
When final volume is fixed, calculate the stock fraction from target OD divided by stock OD. The remainder is diluent. When stock aliquot is fixed, solve instead for the larger final volume.
A target above stock OD would require concentration rather than dilution, so the workbench rejects that request. A target equal to stock OD is a valid no-dilution boundary.
Check the measurement convention
Use comparable wavelengths, blanks, optical paths and instrument processing. A stock reading already corrected for a previous dilution must be identified consistently before another dilution is planned.
This is a volume calculation for a selected experiment, not a growth, inoculation or biological target recommendation.
Follow the numbers
Prepare 10 mL at one quarter of stock OD
- Target/stock OD = 0.2/0.8 = 0.25.
- Stock volume = 10 × 0.25 = 2.5 mL; diluent volume = 10 − 2.5 = 7.5 mL.
- Check: 0.8 × 2.5 = 0.2 × 10 = 2 OD·mL.
The result follows the proportional model; it does not establish a universal relation between OD and cell number.
Quick guide
How to use this calculator
- Choose a required final volume or an aliquot of stock to use.
- Enter matching stock and target OD values with the same measurement convention.
- Read the stock and diluent volumes; the target cannot exceed the stock by dilution alone.
Calculation method
Calculation and interpretation
Reconcile stock and diluent volumes under an explicitly assumed proportional OD–concentration relationship.
ODstock × Vstock = ODtarget × Vfinal; Vdiluent = Vfinal − Vstock
Worked example
Prepare 10 mL at one quarter of stock OD
The result follows the proportional model; it does not establish a universal relation between OD and cell number.
ODstock × Vstock = ODtarget × Vfinal; Vdiluent = Vfinal − Vstock
Supported inputs
Precision and limits
Experimental boundary
This workbench reconciles entered measurements or plans. It does not validate an assay, establish biological effects or replace the protocol and controls for the actual experiment.
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