Dilution Calculator is the C₁V₁ = C₂V₂ equation with the bench details handled. The identity says the amount of solute never changes — concentration times volume before equals concentration times volume after — and solving it for any one unknown is trivial algebra that is nonetheless fumbled daily. Pick what you are solving for (most often V₁, the stock volume to pipette), enter the other three values, and read the recipe: measure this much stock, add this much solvent, reach this final volume at this concentration. Units pass through unchanged, so molar with millilitres or µg/mL with µL both work as long as each pair stays consistent. The tool refuses impossible set-ups — a target above the stock concentration, a final volume smaller than the stock — instead of reporting negative solvent. The serial planner chains equal-factor steps, 1:10 or 1:2, the way plate assays are actually built.
Features
Solves for C₁, V₁, C₂ or V₂ — pick the unknown
Bench recipe: stock to measure and solvent to add
Dilution factor expressed as a 1:n ratio
Serial dilution planner with per-step concentrations
Molar, mass-per-volume, percent and X units supported
Refuses up-dilutions and negative solvent honestly
Sensible significant figures on every result
Everything computed on your device
How to use the Dilution Calculator
Choose which variable to solve for — usually V₁
Enter the other three values in consistent units
Read how much stock to measure and solvent to add
Use the serial planner for step-series like 1:10 ladders
Example
Input
Stock 100 mM · want 50 mL of 10 mM
Output
Measure 5 mL stock + 45 mL solvent — a 1:10 dilution
V₁ = C₂V₂/C₁ = 10×50/100 = 5 mL.
Common errors & troubleshooting
The calculator says the final concentration exceeds the stock. — Dilution can only reduce concentration — C₂ above C₁ needs evaporation or more solute, not water. Check for a units slip; mixing mM with µM is the usual culprit.
Negative solvent to add. — The requested final volume is smaller than the stock volume already implies. Increase V₂ or accept a smaller stock volume — the tool blocks the arithmetic that would hide this.
Results are off by exactly 1000×. — A unit mismatch between the two concentration fields (mM against µM) or the two volumes (mL against µL). The equation never converts units — both sides of each pair must match.
The serial ladder drifts from expected values at the far end. — Each step inherits the previous step's pipetting error, which compounds down the series. For critical low concentrations, prepare an intermediate stock and start a fresh ladder from it.
Frequently asked questions
What does C1V1 = C2V2 actually state?
That the amount of solute is conserved: concentration × volume before dilution equals concentration × volume after. Only solvent is added, so the product cannot change — everything a dilution calculation does follows from that one identity.
How much stock do I need for a target concentration?
V₁ = C₂·V₂ / C₁. For 50 mL of 10 mM from a 100 mM stock: 10 × 50 / 100 = 5 mL of stock, topped up with 45 mL of solvent. The calculator does this with your numbers and states the solvent explicitly.
What is a serial dilution and when is it better?
A chain of equal-factor dilutions — each step dilutes the previous one 1:10, say. It reaches very low concentrations that a single pipetting step cannot deliver accurately, and it is the standard construction for dose-response curves and plate assays.
Do the units need to be molar?
No. The identity is unit-agnostic: any concentration unit against any volume unit works, provided each pair is consistent. mg/mL with µL, percent with litres, X-fold buffer strengths — all fine, and the answer comes back in the same units.
What is a dilution factor?
The ratio C₁/C₂, equal to V₂/V₁ — a 1:10 dilution means the final mixture is ten times the stock volume drawn. Serial steps multiply: three 1:10 steps give a 1:1000 overall factor.
Related tools
Molarity Calculator — Solve molarity, moles or volume for a solution (M = mol/L).