Antibody Dilution Calculator: Working Dilutions Explained

An antibody dilution calculator works out how much antibody stock and diluent are needed to prepare a target working solution. Enter the stock concentration, desired concentration, and final volume; the calculator returns the stock volume and the amount of diluent to add.

Formula

The calculation uses the dilution equation C₁V₁ = C₂V₂. Rearranging gives V₁ = C₂V₂ / C₁, where C₁ is the antibody stock concentration in µg/mL, V₁ is the stock volume in mL, C₂ is the desired working concentration in µg/mL, and V₂ is the final volume in mL.

The calculator reports volumes in microliters. Because 1 mL equals 1,000 µL, its outputs are:

• Stock antibody (µL) = desired concentration × final volume ÷ stock concentration × 1,000
• Diluent (µL) = final volume in mL × 1,000 − stock antibody volume in µL

Concentrations must use the same units, and the final volume must use mL. If the antibody is supplied with a concentration in mg/mL, convert it to µg/mL first: 1 mg/mL = 1,000 µg/mL. This is a volume-dilution calculator, not a calculator for choosing an appropriate antibody concentration for an assay.

Worked Example

Using the calculator’s default values—stock concentration 1,000 µg/mL, target concentration 10 µg/mL, and final volume 1 mL:

1. Stock volume = 10 µg/mL × 1 mL ÷ 1,000 µg/mL = 0.01 mL.
2. Convert to microliters: 0.01 mL × 1,000 = 10.00 µL antibody stock.
3. Diluent volume = 1 mL × 1,000 − 10 µL = 990.00 µL diluent.

Adding 10 µL of stock to 990 µL of diluent gives a final volume of 1 mL at 10 µg/mL, assuming volumes are additive and the stock concentration is accurate.

What an Antibody Dilution Means

Dilution reduces the concentration of an antibody by mixing a measured amount of a concentrated stock with a compatible buffer or other diluent. The final concentration describes the mass of antibody per unit of total solution volume. For example, 10 µg/mL means 10 micrograms of antibody in each milliliter of final solution.

Antibody labels and protocols may instead specify a dilution ratio, such as 1:100. That is a volume ratio: one part stock in 100 parts final mixture, conventionally made by combining one part stock with 99 parts diluent. It does not state a mass concentration unless the stock concentration is also known. A ratio-based dilution and a concentration-based calculation are related, but they are not interchangeable without that information.

When to Use the Calculator

Use the calculator when the stock and target concentrations are known and you need a specified final volume. This commonly applies when preparing a working solution from a stock for a laboratory procedure. Follow the protocol or product instructions for the intended concentration and diluent; the arithmetic cannot determine which concentration is suitable for a particular experiment.

For instance, the default example makes 1 mL of a 10 µg/mL solution from a 1,000 µg/mL stock. If you need a different final volume, change that input while keeping both concentrations the same. The required stock amount changes in direct proportion to final volume: doubling the volume doubles both the antibody and diluent amounts.

Reading and Checking the Result

The first output is the volume of antibody stock to measure. The second is the volume of diluent needed to reach the stated final volume. Add those volumes to obtain the intended total, rather than adding the calculated stock volume to a full volume of diluent.

• Check that the target concentration is lower than or equal to the stock concentration. A target above the stock concentration cannot be made by dilution.
• Check units before calculating. Concentrations expressed in mg/mL and µg/mL must be converted to a common unit.
• Use the intended final volume, not a volume that you plan to add on top of the stock.
• Consider whether the stock volume is measurable with the available pipette. Very small calculated amounts may be difficult to measure accurately; preparing a larger batch or an intermediate dilution may help, if the protocol permits.

Common Mistakes and Limits

A frequent mistake is treating “1:100” as one part antibody plus 100 parts diluent. In the usual final-mixture convention, it means one part in 100 total parts. Another is mixing up concentration and dilution factor: a 1:100 dilution reduces the starting concentration by a factor of 100, but does not itself tell you the final concentration.

The calculation also assumes the stated stock concentration is correct, the materials are mixed uniformly, and volumes can be treated as additive. It does not account for antibody lost on a tube or pipette, changes in activity, buffer compatibility, storage conditions, or assay-specific performance. Follow the relevant protocol and product handling instructions, and use an appropriate diluent. If the stock concentration is given in mass per vial rather than per volume, first determine the concentration from the documented reconstitution volume.

Rounding is another practical limit. The displayed values are rounded to two decimal places in µL; a result smaller than the resolution of your equipment should not be treated as an exact, reliably pipettable amount. Avoid rounding intermediate values if doing a more complex calculation by hand.

Frequently Asked Questions

How do I calculate antibody dilution?
Use C₁V₁ = C₂V₂. Divide the target concentration multiplied by the desired final volume by the stock concentration to find the stock volume, then subtract that volume from the final volume to find the diluent amount.

What does a 1:100 antibody dilution mean?
It generally means one part antibody stock in 100 parts of final solution, such as 10 µL stock in a total of 1,000 µL. Check the protocol’s convention if it defines the ratio differently.

Can I dilute an antibody to a higher concentration?
No. Dilution can only keep the same concentration or lower it. A target concentration higher than the stock would require a more concentrated source or a different preparation method.

How much diluent should I add?
Subtract the antibody stock volume from the desired final volume. For example, if the stock volume is 10 µL and the final volume is 1,000 µL, add 990 µL of diluent.

Can I use mg/mL and µg/mL together?
Not without converting them first. Multiply mg/mL by 1,000 to express it in µg/mL, or convert the other concentration to mg/mL so both use the same units.

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in c | Stock concentration | ug/mL | 1000 | 0
in d | Desired concentration | ug/mL | 10 | 0
in v | Final volume | mL | 1 | 0
out a | Antibody stock needed | uL | d * v / c * 1000 | 2
out b | Diluent needed | uL | v * 1000 - a | 2