Dilution Calculator (C1V1 = C2V2)
Calculate any one variable in a dilution equation. Enter three known values, select what you want to solve for, and click calculate.
Tip: Keep units consistent (for example, mL with mL, or L with L).
What this concentration dilution calculator does
This tool helps you quickly solve dilution problems used in chemistry, biology, medicine, and food labs. Most single-step dilution questions can be solved using the classic equation: C1 × V1 = C2 × V2.
The calculator supports four common use cases:
- Find V1: how much stock solution to pipette.
- Find C1: required stock concentration.
- Find C2: final concentration after dilution.
- Find V2: total final volume needed.
How to use it
Step-by-step
- Select the variable you want to solve for in the dropdown.
- Enter the other three values.
- Choose your concentration and volume units (for readable output).
- Click Calculate.
The calculator also reports the amount of diluent (such as water or buffer) when both stock volume and final volume are available.
Variable definitions
| Symbol | Meaning | Typical unit |
|---|---|---|
| C1 | Initial concentration (stock solution) | mg/mL, M, %, ppm |
| V1 | Volume taken from stock | mL, L, µL |
| C2 | Final desired concentration | Same type as C1 |
| V2 | Final total volume after dilution | Same type as V1 |
Worked example
Example: Prepare 250 mL of 20 mg/mL from a 100 mg/mL stock
Known values: C1 = 100 mg/mL, C2 = 20 mg/mL, V2 = 250 mL. Unknown: V1.
Rearranged formula: V1 = (C2 × V2) / C1
V1 = (20 × 250) / 100 = 50 mL
So you need 50 mL of stock and then add diluent up to 250 mL: 200 mL diluent.
Common dilution scenarios
1) Buffer preparation
Making 1X working buffer from 10X stock is a standard dilution operation in molecular biology labs.
2) Disinfectant preparation
Converting concentrated sanitizer or ethanol stocks into working concentrations for cleaning protocols.
3) Analytical standards
Preparing standard curves requires accurate serial and single-step dilutions for calibration.
Important best practices
- Always keep concentration types consistent (e.g., mg/mL with mg/mL).
- Use the same volume base units for V1 and V2 (e.g., both mL).
- Mix thoroughly after dilution to ensure uniform concentration.
- Label final solutions with concentration, date, and preparer initials.
- If precision matters, use calibrated pipettes or volumetric flasks.
Common mistakes to avoid
- Mixing units unintentionally (µL and mL without conversion).
- Using percentage concentration formats inconsistently (w/v, v/v, w/w).
- Confusing final volume with volume of diluent.
- Entering C2 larger than C1 when trying to dilute (that indicates concentration, not dilution).
Quick FAQ
Can this calculator handle serial dilutions?
This tool solves one dilution step at a time. For serial dilution workflows, run each step sequentially.
What if C2 is greater than C1?
Mathematically valid, but it means concentration rather than dilution. You may need evaporation or a stronger stock.
Do I need to include units in the inputs?
Inputs are numeric only. Units are entered separately for output labels, and you must keep them internally consistent.
Final note
A concentration dilution calculator saves time and reduces mistakes, but final responsibility still depends on correct units, clean technique, and proper documentation. If you are working in regulated or clinical environments, always follow your validated SOPs.