How It Works
This calculator works in 4 steps.
Choose the target unit
Select M, mM, mg/mL, or % w/v.
Enter the target concentration and volume
Type the stock strength and the volume to make.
Enter the molecular weight
Type the MW from the bottle label, including the hydrate form.
Read the mass
The calculator returns grams to weigh and a 3-step dissolve, adjust, and fill plan.
The Formula
The formula multiplies molarity, volume in liters, and molecular weight.
m (g) = M × V (L) × MWm (g) = (% w/v ÷ 100) × V (mL)m (mg) = C (mg/mL) × V (mL)- m:
- Mass of solute
- M:
- Target molarity
- V:
- Final volume
- MW:
- Molecular weight (g/mol)
To make 500 mL of 5 M NaCl, m = 5 × 0.5 × 58.44 = 146.1 g. Dissolve in about 400 mL water, then fill to 500 mL.
Conversion Table
The conversion table gives the mass to weigh for 6 common laboratory stocks.
| Reagent | MW | Target | Volume | Mass to weigh |
|---|---|---|---|---|
| Sodium chloride (NaCl) | 58.44 g/mol | 5 M | 500 mL | 146.1 g |
| Tris base | 121.1 g/mol | 1 M | 1,000 mL | 121.1 g |
| Magnesium chloride hexahydrate | 203.3 g/mol | 1 M | 100 mL | 20.33 g |
| EDTA disodium dihydrate | 372.2 g/mol | 0.5 M | 500 mL | 93.06 g |
| Potassium chloride (KCl) | 74.55 g/mol | 3 M | 250 mL | 55.91 g |
| Glucose | 180.2 g/mol | 1 M | 200 mL | 36.03 g |
What Is the Stock Solution Preparation Calculator?
The Stock Solution Preparation Calculator is a tool that returns the mass of solute to dissolve for a target stock concentration and volume. The calculator multiplies concentration, volume, and molecular weight (MW) to give grams of solid.
A stock solution is a concentrated solution made once and diluted many times. Common stocks include 5 M NaCl, 1 M Tris, and 0.5 M EDTA. The calculator accepts molar, mass, and percent targets, and gives the weighing amount in g and mg along with the preparation steps.
Common Uses
There are 5 main uses of this calculator.
Buffer stocks
Labs make 1 M Tris and 1 M HEPES stocks for many buffers.
Salt stocks
Researchers prepare 5 M NaCl and 1 M MgCl₂.
Media components
Microbiologists prepare 20% glucose and 1 M MgSO₄.
Teaching labs
Students weigh solids for molar solutions.
In-house reagent kits
Core facilities prepare standard stock sets.