Cell-culture working solution
A 2.5 mM stock diluted to 100 uM at 50 mL needs 2 mL stock and 48 mL nominal diluent. The 2 mL transfer should be made with equipment qualified at that range.
Chemistry and laboratory planning
Dilution Conversion Calculator
Convert a stock concentration in mM to a target in uM and calculate the exact stock aliquot, diluent volume, dilution factor, and conserved solute amount.
Chemistry / solution preparation
Turn a concentration target into a pipetting recipe
Use this page for one-step, same-solute dilution when the stock is stronger than the desired solution. It converts the concentration units before solving the recipe, so a 2.5 mM stock and a 100 uM target are not compared as bare numbers.
Stock aliquot-
Diluent to add-
Dilution factor-
Stock share-
Solute amount-
LIVE CURRENT-VALUE ANALYSIS
Aliquot-to-final-volume composition
The vessel partition scales with the current stock and diluent volumes; concentration labels and dilution factor update with every valid input.
| Quantity | Starting value | Operation | Current value | Unit |
|---|
DETAILED CALCULATION PROCESS
Formula, units, current substitution, and reconciliation
1. Governing relation
C1 V1 = C2 V2; DF = C1 / C2; Vdiluent = V2 - V1
Convert C1 and C2 to the same amount-concentration unit, preserve solute amount, then close the final volume. The model assumes the diluent adds no solute and volumes are additive.
2. Symbols and default basis
| Symbol | Meaning | Unit | Default basis |
|---|---|---|---|
| C1 | Stock amount concentration | uM after conversion | 2.5 mM = 2500 uM |
| C2 | Target amount concentration | uM | 100 uM |
| V1 | Stock aliquot | mL | Solved |
| V2 | Final solution volume | mL | 50 mL |
| DF | Dilution factor C1/C2 | dimensionless | 25 |
| n | Conserved amount C x V | nmol | 5000 nmol |
3. Unit normalization
- 1 mM = 1000 uM, so the default 2.5 mM stock is 2500 uM.
- With concentration in uM and volume in mL, the product is nmol.
- The model reports both liquid volumes in mL, avoiding hidden microliter-to-milliliter steps.
4. Current numerical substitution
5. Independent reconciliation
HOW TO USE THIS CALCULATOR
Prepare one stock dilution with an explicit concentration-unit bridge
- Confirm that the stock and target refer to the same solute and chemical form.
- Enter the stock concentration in mM from its label, assay, or certificate.
- Enter the desired working concentration in uM and the intended final volume in mL.
- Read the stock aliquot first, then add diluent until the final volume is reached rather than blindly dispensing the difference.
- Export the recipe with the lot, pipette, vessel, preparation date, and conserved-amount check.
CHEMISTRY FOUNDATIONS
Why C1V1 = C2V2 conserves the target solute
- Dilution conserves solute
- The amount transferred in the aliquot equals the amount present in the finished solution when no reaction or loss occurs.
- Units must match before division
- A numerical ratio between mM and uM is wrong until one concentration is converted.
- Aliquot and final volume are different
- V1 is what leaves the stock container; V2 is the total volume after dilution.
- Dilution factor is not the diluent ratio
- DF = 25 means one part stock in 25 parts final solution, not one part stock plus 25 parts diluent.
- Volumetric technique matters
- For high-accuracy work, transfer stock and make up to a calibration mark because simple liquid-volume addition may not be exact.
DEEP ANALYSIS 1
When a one-step recipe becomes impractical
If V1 falls below the reliable range of the available pipette, prepare an intermediate stock or use a serial dilution. The equation can be correct while the procedure is not defensible.
DEEP ANALYSIS 2
Why concentration uncertainty follows the aliquot
Relative errors in stock assay, aliquot delivery, and final-volume setting propagate into C2. This calculator supplies a nominal recipe, not an uncertainty budget.
DEEP ANALYSIS 3
What target equals stock means
When C2 equals C1, DF = 1, V1 = V2, and diluent is zero. That is a valid no-dilution boundary, useful for checking form wiring.
RESULT INTERPRETATION
Read aliquot, diluent, and dilution factor as one recipe
A larger dilution factor produces a smaller stock fraction; it does not by itself imply better accuracy.
The solute-amount result is a reconciliation value. A mismatch in a manual worksheet usually signals a unit or volume-definition error.
REAL USE CASES
Direct preparation and the no-dilution boundary
No-dilution control
A 0.1 mM stock is already 100 uM. For 10 mL final volume, the model returns 10 mL stock and zero diluent, making the boundary explicit instead of inventing a dilution.
EVIDENCE AND DATA QUALITY
Record the stock assay and every volumetric transfer
Retain the stock identity and lot, certified concentration, target protocol, pipette and volumetric-vessel IDs, actual preparation volume, operator, temperature if volumetric accuracy matters, and the exported amount/volume reconciliation.
LIMITS AND EXCLUSIONS
Where the ideal one-step dilution relation stops
- Applies to one solute whose chemical amount is conserved during mixing.
- Does not model reaction, adsorption, precipitation, evaporation, or degradation.
- Assumes the target is no stronger than the stock.
- Uses nominal additive volumes; high-precision preparations should be made to a final mark.
- Does not propagate stock-assay or glassware uncertainty.
TERMS USED HERE
Vocabulary for aliquots, dilution factors, and final volume
- Stock solution
- Relatively concentrated source solution used to prepare a weaker working solution.
- Aliquot
- Measured portion removed from the stock.
- Diluent
- Solvent or compatible solution added without contributing the target solute.
- Dilution factor
- Ratio of stock concentration to final concentration.
- Final volume
- Total prepared volume, not merely the volume of diluent.
- Amount concentration
- Amount of solute divided by solution volume, commonly expressed in mol/L.
RELIABLE SOURCES
Molarity and amount-concentration references
FREQUENTLY ASKED QUESTIONS
Can the target be higher than the stock? and related questions
Can the target be higher than the stock?
No. Simple dilution cannot increase concentration; concentrate the material or choose a stronger stock.
Why is stock entered in mM but target in uM?
That common laboratory pairing makes the unit conversion visible and prevents comparing 2.5 with 100 as if they shared a unit.
Should I add exactly the reported diluent volume?
For routine nominal work, yes. For calibrated preparation, transfer the stock and bring the vessel to the final-volume mark.
What if the aliquot is too small to pipette?
Use an intermediate dilution designed for a reliable transfer range.
Does density affect this calculation?
Not for the stated amount-concentration/volume model, but nonadditive volumes can matter in concentrated mixtures.
Can I use mass concentration instead?
Only after a defensible conversion using molar mass and chemical form; this page expects amount concentration.
IMPORTANT BOUNDARY
Not a concentration, reaction, or nonadditive-volume model
This nominal recipe does not replace laboratory SOPs, compatibility review, uncertainty analysis, or independent verification for clinical, regulated, or safety-critical preparations.