How It Works
This calculator works in 4 steps.
Enter the starting concentration
Type C₀ in the unit of the final report.
Add each step
Type the step factor, or the transfer and diluent volumes, for every tube.
Multiply in order
The calculator computes each step factor as (V_t + V_d) / V_t and multiplies the factors.
Read the cumulative table
The result lists step factor, cumulative DF, and concentration for each tube.
The Formula
The formula divides the starting concentration by the product of all step factors up to tube n.
Fᵢ = (V_tᵢ + V_dᵢ) / V_tᵢCₙ = C₀ / (F₁ × F₂ × … × Fₙ)- Fᵢ:
- Factor of step i
- V_tᵢ:
- Transfer volume into step i
- V_dᵢ:
- Diluent volume of step i
- C₀:
- Starting concentration
From 500 ng/mL, factors of 2, 5, and 10 give 250, 50, and 5 ng/mL. The cumulative DF after step 3 is 100.
Conversion Table
The conversion table follows a 5-step plan from 500 ng/mL with different factors and volumes at each step.
| Step | Factor | Transfer + diluent | Cumulative DF | Concentration |
|---|---|---|---|---|
| Step 1 | 2 | 100 µL + 100 µL | 2 | 250 ng/mL |
| Step 2 | 5 | 50 µL + 200 µL | 10 | 50 ng/mL |
| Step 3 | 10 | 20 µL + 180 µL | 100 | 5 ng/mL |
| Step 4 | 4 | 50 µL + 150 µL | 400 | 1.25 ng/mL |
| Step 5 | 2.5 | 80 µL + 120 µL | 1,000 | 0.5 ng/mL |
What Is the Variable-Factor Serial Dilution Calculator?
The Variable-Factor Serial Dilution Calculator is a serial dilution tool that applies a different dilution factor at each step and tracks the cumulative factor and concentration through the chain. The user sets each step's factor or each step's transfer and diluent volumes.
Variable steps place concentration points where they matter. A standard curve can use small steps near the expected sample range and large steps at the extremes. The calculator multiplies the step factors in order and flags any step whose transfer volume falls outside a set pipette range.
Common Uses
There are 5 main uses of this calculator.
Uneven standard curves
Analysts space standards closely near the decision limit and widely at the ends.
Kit protocol replication
Users reproduce kit standard schemes such as 1:2, 1:2, 1:4, 1:5.
Range finding
Researchers jump 10-fold first, then refine with 2-fold steps.
Sample-saving schemes
Labs use large first steps to save scarce samples.
Method transfer checks
QC teams verify that a transferred method's step table gives the stated concentrations.