How It Works
This calculator works in 4 steps.
Enter the stock concentration
Type the stock strength in mM or µM.
List the doses
Type each final concentration, including 0 for the vehicle control.
Set the well volume and solvent percent
Type the final well volume and the fixed solvent percent.
Read the volumes
The calculator returns stock volume and solvent backfill for every dose.
The Formula
The formula subtracts each dose's stock volume from the fixed total solvent volume.
V_S = (%S / 100) × V_wellV_stockᵢ = Cᵢ × V_well / C_stockV_backfillᵢ = V_S − V_stockᵢ- %S:
- Fixed solvent percent
- V_well:
- Final well volume
- Cᵢ:
- Final dose i
- C_stock:
- Stock concentration
In a 200 µL well at 0.5% DMSO, the solvent volume is 1 µL. A 30 µM dose from a 10 mM stock uses 0.6 µL stock plus 0.4 µL DMSO backfill.
Conversion Table
The conversion table gives stock and DMSO backfill per 200 µL well for 6 doses from a 10 mM stock at 0.5% DMSO.
| Final dose | Stock volume | DMSO backfill | Final DMSO |
|---|---|---|---|
| 50 µM | 1 µL | 0 µL | 0.5% |
| 30 µM | 0.6 µL | 0.4 µL | 0.5% |
| 10 µM | 0.2 µL | 0.8 µL | 0.5% |
| 3 µM | 0.06 µL | 0.94 µL | 0.5% |
| 1 µM | 0.02 µL | 0.98 µL | 0.5% |
| 0 µM | 0 µL | 1 µL | 0.5% |
What Is the Constant Solvent Assay Calculator?
The Constant Solvent Assay Calculator is a tool that keeps the solvent percent the same in every well of a dose series by adding pure solvent (backfill) to wells that receive less stock. Every well, including the vehicle control, ends at the same solvent percent.
Solvents such as DMSO affect cells and enzymes at levels as low as 0.1% to 1%. A dose series made by adding different stock volumes from one stock gives different solvent levels across wells, which mixes a solvent effect into the dose response. The calculator returns stock and backfill volumes for each dose.
Common Uses
There are 5 main uses of this calculator.
Dose-response plates
Pharmacologists keep DMSO equal across all doses.
Acoustic dispensing
Screening labs program backfill transfers.
Vehicle controls
Users match control wells to treated wells.
Combination studies
Researchers balance solvent from 2 compound stocks.
Assay validation
Developers confirm solvent tolerance at a fixed level.