Guide · dilution factor
Definition
The dilution factor (DF) tells you how much a sample was diluted. If the stock is ten times more concentrated than the final solution, the dilution factor is 10. On this site, DF is also written as 1:N and N×. 1:N means 1 part sample in N parts total. A 1:10 dilution is 1 mL sample plus 9 mL diluent to 10 mL final (not 1 + 10).
Formulas
From concentrations (same kind of unit for C1 and C2):
DF = C1 ÷ C2
From volumes (final volume and aliquot or sample volume):
DF = Vfinal ÷ Valiquot
When you know DF and the final volume, the sample volume and diluent volume are:
Valiquot = Vfinal ÷ DF
Diluent = Vfinal − Valiquot
For repeated steps with the same factor each time:
DFtotal = DF1 × DF2 × …
Worked examples
1:10 buffer dilution
You pipette 1 mL of stock into a tube and bring the volume to 10 mL with diluent. The aliquot is 1 mL and the final volume is 10 mL, so DF = 10 mL ÷ 1 mL = 10× (1:10). You added 9 mL of diluent.
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Hemocytometer trypan blue mix (DF 2)
A common viability check mixes equal volumes of cell suspension and trypan blue before counting. If you combine 1 µL of cells with 1 µL of dye, the final volume is 2 µL and the sample fraction is 1 µL, so DF = 2 µL ÷ 1 µL = 2× (1:2).
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Serial 10-fold dilution (three steps)
Three consecutive 10-fold steps multiply to a total dilution of 10 × 10 × 10 = 1000× (1:1000). Use the serial mode when you only need the product, or Serial Dilution when you need each step concentration and pipette volume.