Understand the relationship
The reasoning behind the result
Conserve the material, change its concentration
C₁V₁ = C₂V₂
The stock aliquot contains concentration C₁ times volume V₁ of the measured material. Adding material-free diluent changes the final volume to V₂ but preserves that amount. The final concentration C₂ must therefore satisfy the volume balance.
A dilution cannot raise concentration. Equal stock and target concentrations give a factor of one and zero added diluent. A target above the stock concentration is rejected instead of producing a negative diluent instruction.
A dilution ratio names the final mixture
V₁ = V₂/DF; Vdiluent = V₂(1 − 1/DF)
A 1:500 dilution here means one stock volume in 500 final volumes: one part stock plus 499 parts diluent. It does not mean one part stock plus 500 parts diluent. The same convention applies when an antibody protocol supplies a dilution ratio.
The output separates those three volumes so you do not accidentally add the final volume as diluent. It also shows the stock fraction, which is the reciprocal of the dilution factor.
Units can be converted only when they measure the same thing
Molar concentrations convert through mol/L; mass concentrations convert through mg/mL. For example, 1 ng/µL equals 1 µg/mL. Converting mass concentration to molar concentration requires a molecular mass and is intentionally outside this dilution balance.
Cell concentrations use the same conservation arithmetic only for a well-mixed suspension with no material loss or population change during preparation. A calculated volume does not choose a seeding target or assess viability.
Follow the numbers
A 100-fold dilution with different displayed units
- Convert 1 mmol/L stock to 1,000 µmol/L.
- DF = 1,000/10 = 100. For V₂ = 1,000 µL, take V₁ = 1,000/100 = 10 µL.
- Add 1,000 − 10 = 990 µL diluent, giving 1,000 µL total at 10 µmol/L.
The conserved amount is 0.01 µmol both before and after dilution.
Quick guide
How to use this calculator
- Choose concentration, fold-dilution or measured-volume input.
- For concentrations, select each unit; conversion is supported within one concentration family.
- Enter the final total volume, which already includes the stock aliquot.
- Read both stock and diluent volumes, and check that the aliquot can be measured reliably.
Calculation method
Calculation and interpretation
Turn the dilution you need into an inspectable stock-and-diluent volume balance.
C₁V₁ = C₂V₂; DF = C₁/C₂ = V₂/V₁; diluent = V₂ − V₁
Worked example
A 100-fold dilution with different displayed units
The conserved amount is 0.01 µmol both before and after dilution.
C₁V₁ = C₂V₂; DF = C₁/C₂ = V₂/V₁; diluent = V₂ − V₁
Supported inputs
Precision and limits
Preparation arithmetic
Volumes are assumed additive and the stock uniformly mixed. The calculation does not choose a solvent, biological target, concentration, incubation condition or validated laboratory protocol. Check compatibility and the working range of the equipment separately.
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