How It Works
This calculator works in 4 steps.
Enter the low and high concentrations
Type the range ends, including 0 for a blank.
Enter the point count
Type the number of levels, such as 5 or 6.
Enter the stock and volume
Type the stock concentration and the volume per level.
Read the series
The calculator lists each level, the step size, and the stock volume per level.
The Formula
The formula adds a constant step to the lowest concentration for each point.
Δ = (C_high − C_low) / (k − 1)Cᵢ = C_low + i × ΔV₁ᵢ = Cᵢ × V / C_stock- Δ:
- Constant step
- C_low / C_high:
- Range ends
- k:
- Point count
- C_stock:
- Stock concentration
- V:
- Volume per level
Five points from 10 to 50 mg/L give Δ = 10 mg/L: 10, 20, 30, 40, and 50 mg/L. From a 1,000 mg/L stock in 100 mL flasks, the 30 mg/L level takes 3 mL of stock.
Conversion Table
The conversion table shows step size and levels for 5 linear series.
| Low | High | Points | Step | Levels |
|---|---|---|---|---|
| 0 | 100 | 6 | 20 | 0, 20, 40, 60, 80, 100 |
| 10 | 50 | 5 | 10 | 10, 20, 30, 40, 50 |
| 0 | 2 | 5 | 0.5 | 0, 0.5, 1, 1.5, 2 |
| 5 | 40 | 8 | 5 | 5, 10, 15, 20, 25, 30 … |
| 0 | 1,000 | 11 | 100 | 0, 100, 200, 300, 400, 500 … |
What Is the Linear Concentration Series Calculator?
The Linear Concentration Series Calculator is a tool that generates concentrations with a constant difference between neighbors, so the points are evenly spaced on a linear axis. The user enters the lowest value, the highest value, and the point count.
Linear spacing suits methods with a straight-line response, such as UV-Vis absorbance under the Beer-Lambert law, HPLC peak area, and titration curves. ICH Q2 guidance asks for at least 5 concentrations for linearity assessment. The calculator returns each level and the stock volume to prepare it independently.
Common Uses
There are 5 main uses of this calculator.
Linearity validation
Validation teams prepare 5 or more levels across 80% to 120% of the test concentration.
Absorbance calibration
Analysts calibrate UV-Vis methods within the linear absorbance range.
HPLC calibration
Chromatographers prepare evenly spaced external standards.
Teaching labs
Instructors run Beer-Lambert experiments with 5 even levels.
Spike recovery levels
Labs spike samples at low, mid, and high levels of a linear range.