Free Online Calculators
Science & Lab Calculators
Precise, free tools for chemistry, biology, and lab work. Calculate solution dilutions, alcohol concentrations, and more — using verified scientific formulas, right in your browser.
All science & lab calculator tools
Click any tool below to open the calculator and get instant, verified results.
C₁V₁ = C₂V₂
Concentration × Volume is conserved
Calculate the volume of stock solution needed to prepare a diluted solution of a desired concentration. Uses the standard C₁V₁ = C₂V₂ equation — the most fundamental formula in solution chemistry. Enter any three values and the calculator solves for the fourth. Supports molar (M), millimolar (mM), percent (%), and mg/mL concentration units, and volumes in mL, µL, or L.
Open calculatorABV₁ × V₁ = ABV₂ × V₂
Pure alcohol volume is conserved
Calculate exactly how much water to add to dilute a high-strength alcohol solution to a target ABV (Alcohol By Volume). Built for craft distillers, home brewers, lab technicians, and anyone working with ethanol. Accounts for volume contraction — a key real-world factor where mixing alcohol and water produces a final volume slightly less than the sum of both — which a generic C₁V₁ = C₂V₂ calculator will miss. Supports ABV % and proof, with volumes in mL, L, and fl oz.
Open calculatorCalculate molar concentration (mol/L) from mass, molecular weight, and volume. Useful for preparing solutions in chemistry and biochemistry labs.
Coming soonConvert between pH, hydrogen ion concentration [H⁺], and pOH values. Includes a colour-coded pH scale reference for acids and bases.
Coming soonThe science behind these calculators
Both tools are built on foundational principles of solution chemistry. Here’s what each formula means and when to use it.
C₁V₁ = C₂V₂
When you dilute a solution, the amount of solute (the dissolved substance) stays the same — only the volume changes. This single equation captures that principle. Solve for any unknown variable by rearranging: V₁ = C₂V₂ ÷ C₁, and so on.
ABV₁ × V₁ = ABV₂ × V₂
For alcohol specifically, pure ethanol volume is conserved during dilution. However, total volume is not simply additive — ethanol and water molecules pack together, causing volume contraction of up to ~3%. Our calculator accounts for this; a generic dilution calculator does not.
Use the Dilution Calculator for:
Use the Alcohol Dilution Calculator for:
Who uses these science & lab calculators?
From research labs to home distilleries, our free tools serve anyone who needs precise concentration calculations.
Lab Technicians
Prepare buffer solutions, reagents, and serial dilution series quickly and accurately.
Students
Verify C₁V₁ = C₂V₂ homework problems and lab report calculations instantly.
Craft Distillers
Proof down spirits to target ABV with precision, accounting for volume contraction.
Brewers & Mixologists
Adjust alcohol concentration in home brews, cocktail bases, and custom spirit blends.
DIY & Herbalists
Dilute high-proof alcohol to the optimal extraction percentage for tinctures and herbal preparations.
Quality Control
Verify concentration calculations before sampling, assaying, or submitting to regulatory compliance checks.
Frequently asked questions
What is the C₁V₁ = C₂V₂ formula and when do I use it?
C₁V₁ = C₂V₂ is the dilution equation, where C = concentration and V = volume. It states that the amount of solute (dissolved substance) is the same before and after dilution — only the total volume changes. Use it any time you need to take a concentrated stock solution and dilute it to a lower concentration. For example: you have a 10 M NaCl stock and need 250 mL of 0.5 M — the formula tells you to take 12.5 mL of stock and top up to 250 mL.
Why should I use the alcohol dilution calculator instead of the regular dilution calculator for spirits?
When ethanol and water are mixed, the resulting total volume is slightly less than the sum of the two — a phenomenon called volume contraction or alcohol contraction. This is because some ethanol molecules fit neatly between water molecules. The generic C₁V₁ = C₂V₂ formula assumes volumes are additive, which is not accurate for alcohol-water mixtures. A dedicated alcohol dilution calculator accounts for this contraction, giving you a more precise result — important when proofing spirits for bottling or legal compliance.
How do I dilute 95% ethanol to 70% for use as a disinfectant?
Use the Alcohol Dilution Calculator above — enter 95% as the starting ABV, 70% as the target ABV, and the volume you have. The calculator will tell you exactly how much water to add. As a rough guide: to make 100 mL of 70% ethanol from 95% stock, you need approximately 73.7 mL of the 95% ethanol topped up to 100 mL with distilled water. Always use distilled or deionised water for lab-grade results.
What concentration units does the dilution calculator support?
The dilution calculator supports molar (M), millimolar (mM), percent by volume (%), and mg/mL units for concentration, with volume inputs in litres (L), millilitres (mL), and microlitres (µL). As long as you keep the concentration units consistent between C₁ and C₂, and the volume units consistent between V₁ and V₂, the formula works correctly.
Is the data I enter into these calculators stored or shared?
No. All calculations run entirely in your browser using JavaScript. No concentration values, volumes, or any other inputs are ever sent to a server, stored in a database, or shared with any third party. This is important for lab environments where reagent concentrations may be proprietary or sensitive.
Are more science and lab calculators planned?
Yes — a Molarity Calculator (mass, molecular weight, and volume to moles/L) and a pH Calculator (pH, pOH, and hydrogen ion concentration) are currently planned for this category. Check back or visit the blog for updates on new tools.
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