How It Works
This calculator works in 3 steps.
Enter the stock concentration (C₁)
Type the labeled concentration of the concentrate, such as 1 M NaCl or 10 mg/mL protein.
Enter the target concentration (C₂) and final volume (V₂)
Type the working concentration in the same unit as C₁ and the total volume to prepare.
Read the stock volume (V₁)
The calculator divides C₂ × V₂ by C₁ and shows V₁ in mL and µL, plus the matching dilution ratio and the diluent volume.
Check pipette range
Compare V₁ with the pipette range on hand. Use an intermediate dilution, if V₁ falls under 1 µL (0.001 mL).
The Formula
The formula divides the solute amount in the final solution by the stock concentration.
V₁ = (C₂ × V₂) / C₁V₁ = V₂ / DF, where DF = C₁ / C₂- V₁:
- Stock volume to transfer
- C₁:
- Stock concentration
- C₂:
- Target concentration
- V₂:
- Final volume
- DF:
- Dilution factor
For 50 mL of 0.5 mg/mL solution from a 10 mg/mL stock, V₁ = (0.5 × 50) / 10 = 2.5 mL (2,500 µL). The dilution factor is 20.
Conversion Table
The conversion table shows the stock volume in mL and µL for 6 combinations of stock strength, target strength, and final volume.
| Stock (C₁) | Target (C₂) | Final volume | Stock volume (mL) | Stock volume (µL) | Ratio |
|---|---|---|---|---|---|
| 1 M | 0.1 M | 10 mL | 1 mL | 1,000 µL | 1:10 |
| 10 mg/mL | 0.5 mg/mL | 50 mL | 2.5 mL | 2,500 µL | 1:20 |
| 100 µM | 1 µM | 1,000 mL | 10 mL | 10,000 µL | 1:100 |
| 5 % | 0.25 % | 200 mL | 10 mL | 10,000 µL | 1:20 |
| 20 mM | 2 mM | 25 mL | 2.5 mL | 2,500 µL | 1:10 |
| 1 M | 0.01 M | 500 mL | 5 mL | 5,000 µL | 1:100 |
What Is the Stock Volume Calculator?
The Stock Volume Calculator is a single-purpose dilution tool that returns the volume of concentrated stock (V₁) required for a chosen final concentration and final volume. The tool fixes the unknown as V₁, so the user enters only the stock concentration, the target concentration, and the target volume.
Stock volume is the first number a technician needs at the bench. The pipette setting, the tube size, and the reagent consumption all follow from V₁. The calculator reports V₁ in milliliters (mL) and microliters (µL) and flags results below 1 µL, where a single transfer loses accuracy.
Common Uses
There are 5 main uses of this calculator.
Pipette setup
Users set a P200 or P1000 pipette to the exact stock volume for one transfer.
Reagent budgeting
Lab managers estimate how much expensive stock, such as an enzyme or antibody, a single preparation consumes.
Microvolume preparation
Scientists find out when a direct dilution needs less than 1 µL of stock and switch to a two-step method.
Supplier label conversion
Users turn a supplier's labeled stock concentration into a practical transfer volume.
Kit protocol scaling
Technicians recalculate stock volume when a kit protocol volume of 10 mL changes to 250 mL (8.45 US fl oz).