Dilution Calculator for ug/µL Concentrations

A dilution calculator for µg/µL works out how much stock solution and diluent are needed to make a target concentration and final volume. Enter the stock concentration, target concentration, and final volume in matching units; the calculator returns stock volume, diluent volume, and the dilution factor.

Formula

The calculation uses conservation of solute: the amount of material in the stock portion equals the amount in the completed solution. The standard equation is C₁V₁ = C₂V₂.

• C₁ is the stock concentration in µg/µL.
• V₁ is the volume of stock solution to use, in µL.
• C₂ is the target concentration in µg/µL.
• V₂ is the final volume of the diluted solution, in µL.

Rearranging gives V₁ = C₂V₂ ÷ C₁. The diluent volume is V₂ − V₁, and the dilution factor is C₁ ÷ C₂. A factor of 5 means the final concentration is one-fifth of the stock concentration. The calculator assumes the stock and target concentrations use the same units, and that the listed final volume includes both stock and diluent.

Worked Example

Using the calculator’s defaults—stock concentration 10 µg/µL, target concentration 2 µg/µL, and final volume 100 µL:

1. Stock volume: (2 µg/µL × 100 µL) ÷ 10 µg/µL = 20 µL.
2. Diluent volume: 100 µL − 20 µL = 80 µL.
3. Dilution factor: 10 µg/µL ÷ 2 µg/µL = 5.

The result is 20 µL of stock plus 80 µL of diluent, making 100 µL at 2 µg/µL. The stock and target concentrations are in µg/µL, so the units cancel correctly in the stock-volume calculation.

What µg/µL Means

µg/µL means micrograms of material per microliter of solution. It is a mass-per-volume concentration, not a measure of the total amount in a tube. For instance, 2 µg/µL in 100 µL contains 200 µg of material; the same concentration in 50 µL contains 100 µg.

Useful equivalent units include 1 µg/µL = 1 mg/mL = 1 g/L. A concentration written as 2 mg/mL can therefore be entered as 2 µg/µL without conversion. If a label instead uses ng/µL, convert before calculating: 1 µg/µL equals 1,000 ng/µL. Mixing these scales without converting can create a thousand-fold error.

How to Use the Calculator

• Enter the stock concentration shown for the solution you have.
• Enter the concentration you want the final mixture to have.
• Enter the total final volume, not just the volume of diluent.
• Use the displayed stock volume and diluent volume to prepare the mixture, subject to the precision of your measuring equipment.

The inputs must be physically possible: the target concentration should be positive and no greater than the stock concentration, and the final volume must be at least as large as the calculated stock volume. If the target equals the stock concentration, the calculation gives no diluent. A target above the stock concentration cannot be reached by dilution; it requires a more concentrated starting material or a different preparation method.

Measurement, Rounding, and Common Errors

Calculator output is mathematical precision, not a promise that a pipette or other measuring tool can dispense that exact volume. Check the instrument’s stated range and resolution, and avoid reporting more decimal places than the measurement supports. For very small stock volumes, it may be more reliable to make an intermediate dilution and then prepare the final mixture from that working solution. Calculate each stage separately, keeping track of the concentration after every step.

• Confusing final volume with diluent volume: if the target is 100 µL total, add stock and diluent to make 100 µL altogether; do not add 100 µL of diluent on top of the stock.
• Mixing units: convert both concentrations to the same unit before using C₁V₁ = C₂V₂. Convert volume units too if you choose units other than µL.
• Using a mass instead of a concentration: a value such as 10 µg is a total amount, not 10 µg/µL. You need the stock solution’s volume to determine its concentration.
• Ignoring the material being added: a solvent, buffer, or other ingredient that contributes volume should be included in the final-volume plan.

Limits and Practical Considerations

This calculator assumes the material is evenly distributed, no material is lost or degraded, and volumes are additive. Real mixtures can depart from these assumptions because of evaporation, incomplete mixing, adsorption to surfaces, or changes in volume when components are combined. The equation calculates the intended concentration from the inputs; it does not verify a solution’s actual concentration or account for chemical compatibility, stability, or preparation conditions.

Use a suitable diluent for the specific material and follow the applicable laboratory procedure. Label prepared solutions with the concentration and relevant preparation details, and avoid relying on a calculated value when the stock concentration is uncertain. The calculation itself is the same whether volumes are recorded in µL or mL, as long as all volume values use one consistent unit.

Frequently Asked Questions

How do I calculate a dilution in µg/µL?
Use C₁V₁ = C₂V₂. Multiply the target concentration by the desired final volume, then divide by the stock concentration to find the stock volume. Subtract that volume from the final volume to find the diluent amount.

Is µg/µL the same as mg/mL?
Yes. The numerical values are identical: 1 µg/µL equals 1 mg/mL. Thus 3 µg/µL is the same concentration as 3 mg/mL.

Do I enter the final volume or the amount of diluent?
Enter the total final volume, including the stock solution. The calculator separately finds the amount of diluent to add.

Can I dilute to a concentration higher than the stock?
No. Adding diluent lowers concentration or leaves it unchanged if none is added. To reach a higher concentration, you need a more concentrated stock or another suitable preparation method.

What if my stock is listed in ng/µL?
Convert it to µg/µL first by dividing the numeric value in ng/µL by 1,000. For example, 500 ng/µL equals 0.5 µg/µL.

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in stock | Stock concentration | µg/µL | 10 | 0
in target | Target concentration | µg/µL | 2 | 0
in final | Final volume | µL | 100 | 0
out stockvol | Stock solution needed | µL | target * final / stock | 2
out diluent | Diluent needed | µL | final - stockvol | 2
out factor | Dilution factor | x | stock / target | 2