Stock Solution
Dilution Calculator
Prepare working solutions from concentrated stock. Calculate the exact volume of stock to pipette and diluent to add for any target concentration and volume.
What Is a Dilution of Stock Solution Calculator?
A dilution of stock solution calculator determines the volume of concentrated stock to pipette and the volume of diluent to add when preparing a working solution. Stock solutions are highly concentrated preparations stored in the lab — 10× PBS, 1 M Tris, 5 M NaCl, 10 mM drug stocks in DMSO. This tool applies C₁V₁ = C₂V₂ to produce an exact recipe: pipette V₁ of stock, add (V₂ − V₁) of diluent.
Benefits
- Calculates pipette volume from stock concentration
- Shows exact diluent volume to add
- Handles any stock concentration format
- Generates preparation recipe for lab notebooks
Applications
- Buffer preparation from concentrated stock solutions
- Drug working solution preparation from DMSO stocks
- Media supplement addition from concentrated stocks
- Teaching lab solution preparation exercises
Stock solutions save time, reduce weighing errors, and ensure consistency. A lab maintains a 5 M NaCl stock and dilutes as needed — rather than weighing NaCl for every experiment. Common stock concentrations are designed for simple dilution: 10× stocks dilute 10-fold, 100× stocks dilute 100-fold. Suppliers like Sigma-Aldrich, Thermo Fisher, and Bio-Rad sell ready-made stock solutions at these convenient concentrations. This stock solution dilution calculator converts stock concentration to pipette volumes for any target.
Diluting a Stock Solution
Diluting a stock solution uses V₁ = (C₂ × V₂) ÷ C₁ — the most common rearrangement of C₁V₁ = C₂V₂. V₁ is the volume of stock to pipette, C₁ is the stock concentration (from the bottle label), C₂ is the desired working concentration, and V₂ is the total volume you need.
Rearrange the equation to solve for any unknown:
V₁ = (C₂ × V₂) ÷ C₁— how much stock to pipetteC₂ = (C₁ × V₁) ÷ V₂— what concentration you'll getV₂ = (C₁ × V₁) ÷ C₂— total volume neededThe diluent volume is simply V₂ − V₁. For a 10× stock diluted to 1× in 100 mL: V₁ = (1 × 100) ÷ 10 = 10 mL of stock. Diluent = 100 − 10 = 90 mL. This is the most intuitive dilution calculation — and the most frequently performed in any laboratory.
Stock Solution Dilution Factor
The dilution factor for stock solutions equals C₁ ÷ C₂ = V₂ ÷ V₁. A 10× stock diluted to 1× has a factor of 10. The stock concentration is always greater than the working concentration (C₁ > C₂), so the factor is always greater than 1.
Standard stock dilution factors in biology: 10× PBS → 1× (factor 10), 100× penicillin-streptomycin → 1× (factor 100), 1000× IPTG → 1× (factor 1000). In chemistry: 18 M H₂SO₄ → 1 M (factor 18), 12 M HCl → 0.1 M (factor 120). Each factor tells you what fraction of the final volume comes from stock versus diluent.
Step-by-Step Dilution of Stock Solution Calculator Guide
Follow these steps to calculate your dilution:
Serial Dilution from Stock
Serial dilution from a stock creates multiple working concentrations in one preparation session. Instead of calculating each concentration independently from the stock, prepare the highest concentration first, then serially dilute to get the lower ones.
This approach minimizes pipetting from the precious stock solution and ensures consistency across the concentration range. Enzyme kinetics experiments (Lineweaver-Burk plots), drug dose-response curves, and calibration standard preparation all benefit from serial dilution from a single stock. This stock solution dilution calculator generates both the initial dilution from stock and the subsequent serial dilution concentrations.
Dilution of Stock Solution Calculator Example
Problem: A researcher needs to prepare 50 mL of 1× TAE running buffer from a 50× TAE stock (Sigma-Aldrich T9650) for agarose gel electrophoresis.
V₁ = (C₂ × V₂) ÷ C₁V₁ = (1 × 50) ÷ 50 = 1 mLWater = 50 − 1 = 49 mLDF = 50 ÷ 1 = 50× dilutionFrequently Asked Questions
Calculate V₁ = (C₂ × V₂) ÷ C₁, then add V₂ − V₁ diluent. V₁ is the volume of stock to pipette, C₁ is the stock concentration, C₂ is the target working concentration, and V₂ is the total volume you need. For 100 mL of 1× PBS from 10× stock: V₁ = (1 × 100) ÷ 10 = 10 mL stock + 90 mL water. This stock solution dilution calculator handles all unit combinations and shows every step.
Weigh the calculated mass, dissolve in solvent, and adjust to final volume. Mass (g) = molarity (M) × volume (L) × molecular weight (g/mol). For 100 mL of 1 M NaCl: mass = 1 × 0.1 × 58.44 = 5.844 g. Dissolve in ~80 mL water, then fill to 100 mL in a volumetric flask. Filter-sterilize if needed. Label with concentration, date, lot, and expiration. Store per reagent requirements (room temp, 4°C, or −20°C).
It depends on the reagent. Inorganic salt stocks (NaCl, KCl, MgCl₂) are stable for months at room temperature. Buffer stocks (Tris, HEPES, PBS) are stable for weeks to months at 4°C, longer if filter-sterilized. DMSO compound stocks are stable for months at −20°C. Enzyme stocks lose activity over weeks even at −20°C. Antibiotics in solution degrade faster than dry powder — ampicillin stock lasts ~1 month at −20°C. Always check the manufacturer datasheet (Sigma-Aldrich, Fisher, Bio-Rad) for compound-specific storage recommendations and expiration dates.