Diluent volume for a target concentration
Start from the concentration you want. The calculator works backwards to the diluent volume and fills the vial to that line.
These tools do not provide dosing guidance and are not for human or veterinary use. They are for research-use laboratory calculations only. Verify every result independently.
Diluent for a target concentration
How much diluent gives a chosen stock concentration.
diluent (mL) = vial contents (mg) ÷ target concentration (mg/mL)
Vial fills to the diluent line
How it works
Sometimes the concentration is the fixed point: a protocol calls for a 2 mg/mL stock, and the question is how much diluent gets a given vial there. That is the reconstitution formula rearranged: volume equals mass divided by target concentration.
The result is also given in microlitres, because small diluent volumes are often measured with a pipette rather than a syringe.
Step by step
- Read the vial mass in milligrams.
- Choose the target stock concentration in mg/mL.
- Divide mass by target concentration to get the diluent volume in mL.
- Multiply by 1,000 for µL.
Frequently asked
Divide the vial mass by 2. A 10 mg vial needs 10 ÷ 2 = 5 mL of diluent; a 5 mg vial needs 2.5 mL.
Vial capacities vary; a common research vial holds 2 to 10 mL. If the calculated volume exceeds the vial, split the material or accept a stronger stock and dilute later.
Volumes that small are difficult to measure and the resulting concentration is very sensitive to a tiny error. The warning is a measurement caution, not a prohibition.
Diluent (mL) = vial contents (mg) ÷ target concentration (mg/mL).