What Is a Dilution Calculator and How Does It Work?
A dilution calculator finds an unknown concentration or volume when a stock solution is diluted with solvent, using the relationship that the amount of solute stays constant before and after dilution. It solves for stock volume, final volume, or either concentration when the other three values are known.
The dilution formula is: C₁V₁ = C₂V₂, where C₁ is the stock (initial) concentration, V₁ is the volume of stock solution used, C₂ is the desired final concentration, and V₂ is the desired final volume. Rearranged for the most common use case, the volume of stock needed is V₁ = (C₂ × V₂) ÷ C₁.
According to the CDC's guidance on disinfectant preparation, household bleach (typically 5.25%–8.25% sodium hypochlorite) must be diluted to around 0.1% (1000 ppm) for standard surface disinfection — a calculation this tool performs directly by entering the stock and target percentages.
How to Use This Dilution Calculator
Choose the value you need to solve for, pick matching concentration and volume units, then fill in the remaining three fields. The result — plus the exact amount of diluent (solvent) to add — updates instantly.
- Solve For: The unknown value — most often the volume of stock solution (V₁) needed to reach a target concentration.
- C₁ (Stock Concentration): The concentration of your starting/undiluted solution, in any consistent unit (M, mg/mL, %, or fold/x).
- C₂ (Final Concentration): The concentration you want after dilution — must use the same unit type as C₁.
- V₁ (Stock Volume): The volume of stock solution measured out before adding solvent.
- V₂ (Final Volume): The total volume of the finished, diluted solution.
Because C₁V₁ = C₂V₂ is a ratio, this calculator works with any unit system worldwide — molar (mol/L), mass concentration (mg/mL, µg/mL), percent (%/v), or fold dilution (x) — as long as C₁ and C₂ share the same unit and V₁ and V₂ share the same unit.
What Common Dilution Ratios Mean
Dilution factor (V₂ ÷ V₁) is often written as a ratio, such as 1:10 or 1:100. The table below shows how common lab, medical, and household dilution ratios translate to a fold-change in concentration.
| Dilution Ratio | Fold Reduction | Typical Use |
|---|---|---|
| 1:2 | 2x | Serial dilution series for titration |
| 1:10 | 10x | Standard lab stock dilution |
| 1:100 | 100x | Antibody / reagent working solutions |
| 1:50 (bleach) | ~50x | Household disinfectant from 5.25% stock to ~0.1% |
| 1:200 | 200x | Hydroponic nutrient concentrate to working strength |
Frequently Asked Questions
How do I calculate how much stock solution to use?
Use V₁ = (C₂ × V₂) ÷ C₁: multiply the desired final concentration by the desired final volume, then divide by the stock concentration. For example, to make 5 mL of a 1x solution from a 10x stock, V₁ = (1 × 5) ÷ 10 = 0.5 mL of stock, topped up with 4.5 mL of diluent.
How accurate is this dilution calculator?
This calculator applies the exact C₁V₁ = C₂V₂ algebraic relationship, so results are as accurate as the concentration and volume values you enter. Real-world accuracy also depends on pipette or measuring-cup precision and on C₁ and C₂ being expressed in matching units.
What is the difference between a dilution factor and a dilution ratio?
A dilution factor (e.g., 10x) expresses the total final volume as a multiple of the stock volume used. A dilution ratio (e.g., 1:10) expresses stock volume to total final volume, or sometimes stock to diluent — always check which convention a source is using, since 1:10 stock-to-diluent and 1:10 stock-to-final give different results.
How do I do a serial dilution?
Run this calculator once per step, using the final volume (V₂) of one dilution as the starting volume basis for the next. The overall dilution across all steps equals the product of each individual step's dilution factor — three sequential 1:10 dilutions give a total dilution of 1:1000.