How It Works
This calculator works in 3 steps.
Enter the fold value
Type the fold number, such as 5 for a 5-fold dilution.
Enter the final volume
Type the total volume to prepare, such as 100 µL (0.1 mL).
Enter the starting concentration (optional)
Type C₁ to get the diluted concentration.
Read the volumes and result
The calculator divides the final volume by the fold for the stock volume and divides C₁ by the fold for C₂.
The Formula
The formula divides the final volume and the starting concentration by the fold value.
V_stock = V_final / FoldC₂ = C₁ / FoldFold_total = Fold₁ × Fold₂- Fold:
- Fold dilution (equals DF)
- V_final:
- Final volume
- C₁ / C₂:
- Starting and diluted concentrations
A 20-fold dilution to 100 µL uses 5 µL sample and 95 µL diluent. A 2 mg/mL protein becomes 0.1 mg/mL (100 µg/mL).
Conversion Table
The conversion table lists stock and diluent volumes for 7 fold values at a 100 µL final volume.
| Fold | Stock (per 100 µL) | Diluent | Fraction left | Strength left |
|---|---|---|---|---|
| 2-fold | 50 µL | 50 µL | 0.5 | 50% |
| 3-fold | 33.33 µL | 66.67 µL | 0.3333 | 33.33% |
| 5-fold | 20 µL | 80 µL | 0.2 | 20% |
| 10-fold | 10 µL | 90 µL | 0.1 | 10% |
| 20-fold | 5 µL | 95 µL | 0.05 | 5% |
| 100-fold | 1 µL | 99 µL | 0.01 | 1% |
| 1000-fold | 0.1 µL | 99.9 µL | 0.001 | 0.1% |
What Is the Fold Dilution Calculator?
The Fold Dilution Calculator is a tool that converts a fold-change instruction, such as "dilute 5-fold", into stock and diluent volumes for a chosen final volume. A 5-fold dilution reduces the concentration to one-fifth, so 1 part stock is brought to 5 parts total.
Fold language is standard in molecular biology, pharmacology, and assay development. "5-fold" equals a dilution factor of 5 and a stock-to-final ratio of 1:5. The calculator states each equivalent form, so fold instructions match DF-based and ratio-based protocols.
Common Uses
There are 5 main uses of this calculator.
Sample preparation
Technicians dilute a sample 10-fold to fit the instrument's linear range.
qPCR template dilution
Molecular biologists dilute cDNA 5-fold or 10-fold before amplification.
Pharmacology series
Pharmacologists build 3-fold or half-log steps for dose-response curves.
Dilution linearity tests
Validation teams compare 2-, 4-, and 8-fold dilutions of one sample.
Assay range fitting
Users bring an over-range sample back into the standard curve range.