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Dilute with confidence using our free online solution dilution calculator. Enter any three of stock concentration (C1), stock volume (V1), final concentration (C2), final volume (V2) — leave the unknown blank — and solve via C1×V1=C2×V2 with full unit support for M, mM, %, mg/mL, L, mL, and µL.
Solve DilutionInteractive Solution Dilution Calculator
Enter any three values and leave the unknown blank.
Dilution Result
How the Dilution Calculator Works
Three knowns, one unknown — the conservation of solute does the rest.
Enter Three Values
Type your stock concentration (C1), target concentration (C2), and either the stock volume to pipette (V1) or the final volume (V2). Choose units from the dropdowns.
Leave One Blank
The empty field is what gets solved. Most common: leave V1 blank to find how much stock to pipette for your target.
Get the Answer Plus Diluent
Beyond the solved value, you get the dilution factor (e.g., 1:10) and exactly how much diluent (water/buffer) to add: V2 − V1.
Check the Worked Equation
Every result shows the substituted C1×V1=C2×V2 equation so you can verify the math before touching a pipette.
Dilution Formulas
The dilution equation expresses a conservation law: the moles (or mass) of solute before dilution equal the moles after. Only the volume changes.
The Dilution Equation
Stock concentration times stock volume equals final concentration times final volume.
Volume of Stock to Use
Example: to make 100 mL of 0.1 M from 1.0 M stock: V1 = (0.1 × 100) ÷ 1.0 = 10 mL of stock, plus 90 mL diluent.
Resulting Concentration
Example: 10 mL of 1.0 M stock brought to 100 mL gives C2 = (1.0 × 10) ÷ 100 = 0.1 M.
Dilution Factor
A 10 mL → 100 mL dilution is a 10-fold (1:10) dilution. Serial 1:10 dilutions multiply: three in a row = 1:1000.
Unit Rule
C1 and C2 must be in compatible concentration units, and V1 and V2 in compatible volume units. Molar units (M, mM, µM) interconvert freely; mass units (% w/v ↔ mg/mL) interconvert freely (1% = 10 mg/mL). Do not mix molar with mass units without the solute's molar mass — the calculator will warn you.
Concentration Unit Conversions
| Conversion | Factor | Example |
|---|---|---|
| 1 M → mM | × 1000 | 0.1 M = 100 mM |
| 1 mM → µM | × 1000 | 0.5 mM = 500 µM |
| 1% w/v → mg/mL | × 10 | 0.9% saline = 9 mg/mL NaCl |
| 1 mg/mL → % w/v | ÷ 10 | 20 mg/mL = 2% w/v |
| 1 L → mL | × 1000 | 0.1 L = 100 mL |
| 1 mL → µL | × 1000 | 0.5 mL = 500 µL |
Dilution in the Lab: Practical Guide
Always Add Stock to Diluent
Pipette the calculated V1 of stock into a container, then add diluent up to V2 — not the reverse. Adding V2−V1 of diluent to V1 of stock gives the same total only if volumes are additive, which holds for dilute aqueous solutions.
Mind Significant Figures
A P1000 pipette delivering 10.0 mL is ±0.6% — fine. Delivering 0.10 mL with the same pipette is ±6% — remake the stock or do a serial dilution instead. The calculator's answer is exact; your pipette is not.
Buffer Dilutions
Diluting a buffer changes its pH slightly (activity effects) and dilutes every component equally. For critical work, prepare working buffers from concentrates using this equation, then verify pH.
Cell Culture Media
Antibiotics (e.g., 100× pen-strep → 1×), growth factors in µg/mL, and drug stocks in mM all run through C1V1=C2V2 daily. Keep stocks at round-number concentrations (10 mM, 1 mg/mL) so the mental math stays trivial.
Reference: dilution equation on Wikipedia.
Molarity, Molality, and Mass Percent: Choosing Units
Molarity (M) is the default in most labs, but it is not always the best unit — and the calculator's unit family rule exists for a reason.
When Molarity Shines
Reactions balance in moles, so molarity makes stoichiometry trivial: 1 L of 1 M contains exactly 1 mol. Use M/mM/µM for reaction planning, titrations, and anything where mole ratios matter.
When Mass Units Win
Weighing is more precise than volumetric glassware for small masses, and mass units (% w/v, mg/mL) do not change with temperature — molarity does, because liquids expand when warm. Pharmaceutical formulations and food science lean mass-based for this reason.
Molality: The Temperature-Proof Molar Unit
Molality (mol/kg solvent) keeps the mole logic of molarity without the temperature dependence. It dominates in physical chemistry (freezing-point depression, boiling-point elevation) but is rare on reagent bottles — which is why this calculator focuses on M and mass units.
Converting Between Families
Mass ↔ molar conversion needs the solute's molar mass (MW): M = (% w/v × 10) ÷ MW. For NaCl (MW 58.44): 0.9% saline = (0.9 × 10) ÷ 58.44 = 0.154 M. Keep a MW table taped inside your lab notebook — you will use this weekly.
| Unit | Definition | Temperature Dependent? | Best For |
|---|---|---|---|
| Molarity (M) | mol solute / L solution | Yes | Reactions, titrations |
| Molality (m) | mol solute / kg solvent | No | Colligative properties |
| % w/v | g solute / 100 mL solution | Slightly | Pharma, saline |
| mg/mL | mg solute / mL solution | Slightly | Drug dosing |
Solution Dilution FAQs
It is the dilution equation: stock concentration (C1) times stock volume (V1) equals final concentration (C2) times final volume (V2). It works because dilution adds solvent, not solute — the amount of solute is conserved.
Use V1 = (C2 × V2) ÷ C1. For 100 mL of 0.1 M from 1 M stock: (0.1 × 100) ÷ 1 = 10 mL of stock, then add 90 mL of diluent.
Not directly — converting between them needs the solute's molar mass (M = (% × 10) ÷ MW). Keep C1 and C2 in the same unit family: both molar (M/mM/µM) or both mass-based (%/mg/mL). The calculator enforces this.
1 part stock + 9 parts diluent = 10 parts total, so C2 = C1 ÷ 10 and V2 = 10 × V1. A 1:10 followed by another 1:10 is 1:100 total (dilution factors multiply).
Dilution shifts ionic strength and activity coefficients, nudging pH — usually by 0.05–0.2 units for 10-fold dilutions. The concentration math is still exact; just re-check pH after diluting critical buffers.
V1 = (70 × 1000) ÷ 95 = 736.8 mL of 95% ethanol, then add water to 1000 mL total. (Note: ethanol-water volumes are not perfectly additive, so "to final volume" matters more than adding exactly 263.2 mL water.)
Dilution factor (DF) = V2/V1, e.g., 10 for a 1:10. "1:10 dilution ratio" is ambiguous in some fields — it can mean 1+9 or 1+10 — so DF is the safer number to quote. This calculator reports DF explicitly.
Add stock to a vessel, then bring up to the final volume with diluent. This "to final volume" technique is more accurate than adding a pre-measured diluent volume, especially where mixing is non-ideal.
Worked Example: Antibiotic Stock to Working Concentration
You have a 50 mg/mL ampicillin stock and need 200 mL of LB agar at 100 µg/mL (0.1 mg/mL). How much stock?
Step 1: Convert units — C1 = 50 mg/mL, C2 = 0.1 mg/mL, V2 = 200 mL, solve V1.
Step 2: V1 = (0.1 × 200) ÷ 50 = 0.4 mL = 400 µL.
Step 3: Add 400 µL stock to ~199.6 mL molten agar (add before it solidifies, below 50 °C).
Step 4: Dilution factor = 200 ÷ 0.4 = 500-fold.