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qPCR Dilution Concentration Calculator

The qPCR Dilution Concentration Calculator determines the concentration of a diluted qPCR template or standard from a known starting concentration, the volume transferred, and the final mixture volume. It is useful when preparing standard-curve points, adjusting a template to a working concentration, or checking a manual dilution before pipetting.

The calculation follows conservation of analyte: the amount transferred from the starting solution is spread through the final volume. Along with the final concentration, the page reports the effective dilution factor and the amount of diluent required, so the planned mixture can be checked from more than one angle. Use consistent concentration units throughout; the default labels use copies per microliter, but the ratio calculation also works for another concentration unit if both concentration values use that same unit.

Calculator inputs

copies/µL
µL
µL
Result
—
final concentration
Dilution factor—
Diluent volume—
Copies transferred—

1. Enter the starting concentration
Use the measured or assigned concentration of the qPCR template or standard before dilution.

2. Enter the transferred template volume
Specify how many microliters of the starting solution will be added to the dilution.

3. Enter the final volume
Use the total volume after diluent is added, not just the diluent volume.

4. Review the result
The main value is the final concentration; the breakdown also shows dilution factor, diluent volume, and the number of copies transferred.

Formula:

Final concentration = Starting concentration × (Template volume ÷ Final volume)

Dilution factor = Final volume ÷ Template volume
Diluent volume = Final volume − Template volume

All volumes must use the same unit. The calculation assumes the transferred material mixes uniformly and that analyte loss is negligible.

What the result means

The main result is the expected concentration after the specified aliquot is brought to the chosen final volume.

This is a volumetric dilution calculation; it does not correct for pipetting uncertainty, adsorption losses, or qPCR amplification efficiency.

Given: A standard is 2,500,000 copies/µL. Transfer 4 µL and bring the mixture to 40 µL.

Calculation:
Final concentration = 2,500,000 × (4 ÷ 40) = 250,000 copies/µL.
Dilution factor = 40 ÷ 4 = 10×.
Diluent volume = 40 − 4 = 36 µL.

Result: 250,000 copies/µL after a 10× dilution.

The 4 µL aliquot contains 10,000,000 copies, which are distributed through the 40 µL final volume.

Can I use ng/µL instead of copies/µL?

Yes. The dilution equation is unit-independent as long as the starting and resulting concentrations are expressed in the same concentration unit.

What should I enter for final volume?

Enter the complete mixed volume after the sample and diluent are combined. For example, 2 µL sample plus 18 µL diluent means a 20 µL final volume.

Why must final volume be at least the template volume?

A dilution cannot have less total volume than the aliquot placed into it. If the intended process is concentration rather than dilution, this model is not appropriate.

Does this account for serial dilutions?

The page calculates one dilution step. For a serial dilution, apply each step in sequence or multiply the individual dilution factors.

Is dilution factor the same as fold dilution?

Here they are treated the same way: final volume divided by transferred stock volume. A 10× dilution means one part stock is present in ten parts total mixture.