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Nucleic Acid Copy Concentration and Ideal PCR Doubling

Estimate copies per microliter from a nucleic-acid mass concentration and average unit weight, with a separate ideal-PCR model.

Formula & worked example
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How to use this calculator

Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
Use the worked example to check the method. Reset restores the starting fields.

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Formula and method

A 660 ng/µL dsDNA solution of 1000 bp molecules gives 6.02214 × 10¹¹ copies/µL. Independently, 10 × 10⁷ starting copies/µL with three ideal doubling cycles gives 80 × 10⁷ copies/µL.

Copies/µL = concentration_ng/µL × 6.02214×10²³/(length × 10⁹ × average unit molar mass); amplified copies/µL = initial copies/µL × 2^cycles.

Worked example

Enter these known values and leave the other values blank.

Nucleic-acid mass concentration: 660 ng/µl
Template length (bp for dsDNA; nt for single strands): 1000 bp
Initial DNA copies: 10 × 10⁷ copies/µl
Ideal doubling exponent / cycle count: 3

DNA copies: 60221 × 10⁷ copies/µl
DNA copies after PCR cycle(s): 80 × 10⁷ copies/µl

Assumptions and limitations

Enter mass concentration in ng/µL. The copy result is a number concentration in copies/µL. The default result selector shows multiples of 10⁷; it is not the total sampled copy count.
The average weights are 330 g/mol per ssDNA nucleotide, 340 per ssRNA nucleotide and 660 per dsDNA base pair. Sequence composition and terminal chemistry are not modeled.
The Avogadro constant is the captured rounded 6.02214×10²³ mol⁻¹. The estimate is not a sequence-specific molecular-weight calculation.
PCR is a separate ideal 100-percent-efficiency doubling model without plateau, degradation or sampling loss. Its initial-copy input is not automatically linked to the mass result.
Template length must be a positive whole number. The ideal doubling exponent supports positive values up to 100, including fractional equivalent-cycle inverses; actual PCR runs use whole cycles. Mass concentration and initial copy concentration must be positive.

Common questions

Is the input a total sample mass?

No. It is a concentration in ng/µL; the output is copies/µL. Multiply by sampled microliters if you need a total copy count.

Will real PCR double on every cycle?

Usually not throughout the whole run. This is an ideal theoretical model.

References

Declare the physical or stated approximation domain; captured arithmetic is unchanged.

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