⚗️ Lab Calculators
Stock Solution Calculator
Calculate exactly how to prepare a stock solution from dry powder or liquid reagent. Get mass to weigh or volume to measure, with step-by-step instructions.
How to Use the Stock Solution Calculator
Select your reagent type — Dry Powder (solid reagent) or Liquid Reagent (concentrated liquid). Enter the desired stock concentration, final volume, and molecular weight. For liquid reagents, also enter the concentration and density of the commercial reagent. Click Calculate for a complete recipe with step-by-step instructions.
Key Formulas
Powder: mass (g) = Molarity (M) × Volume (L) × MW (g/mol) / (Purity/100)
Liquid: Volume (mL) = [Desired M × Vol (L) × MW] / [% × density × 10]
Examples
Example 1 — Powder (Tris Base)
Prepare 100 mM Tris in 50 mL.
MW = 121.14 g/mol
mass = 0.1 × 0.05 × 121.14 = 0.606 g
Example 2 — Powder (NaCl)
Prepare 1 M NaCl in 500 mL.
MW = 58.44 g/mol
mass = 1 × 0.5 × 58.44 = 29.22 g
Example 3 — Liquid (HCl 37%)
Prepare 1 M HCl in 100 mL from 37% HCl.
MW = 36.46, density = 1.19
Vol = 8.27 mL of conc. HCl
Example 4 — Liquid (Acetic Acid)
Prepare 1 M acetic acid in 100 mL from glacial acetic acid (100% v/v, density 1.049).
Vol = 5.72 mL
About Stock Solutions in Biotechnology
A stock solution is a concentrated solution prepared in advance and stored, from which working dilutions are made as needed. Preparing stock solutions saves time, reduces weighing errors and ensures consistency across experiments.
Common stock solutions in biotechnology include 1 M Tris-HCl (pH 8.0), 0.5 M EDTA, 5 M NaCl, 10% SDS, 10× PBS and 1 M DTT. These are prepared at high concentration (10× to 100×) and diluted to working concentration before use.
⚠️ Safety with concentrated acids
Always add acid to water, never water to acid. Work in a fume hood when handling concentrated HCl, H₂SO₄ or acetic acid. Wear appropriate PPE.
🧂 Purity matters
If your reagent is less than 100% pure, enter the actual purity percentage. The calculator will adjust the mass to weigh accordingly.
❄️ Storage tips
Label all stocks with: reagent name, concentration, solvent, date prepared, and your initials. Store at 4°C, −20°C or RT as appropriate for the reagent.
📋 Filter sterilise if needed
For cell culture stocks, filter through a 0.22 µm membrane after preparation. Do not autoclave heat-sensitive reagents (EDTA, DTT, antibiotics).
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