LabReadyTools

DNA / RNA Concentration Calculator

M ≈ length × MW per base, c = ρ / M, n = c × V

Approximate nucleic-acid molarity from length and concentration, and convert between ng and pmol.

Inputs

Supply a volume to get the amount in pmol.

g/mol

Average anhydrous MW per bp (sodium salt), + 36.04 g/mol for the 5′ terminal OH groups.

Result

80.9067 nM

≈ 1.61813 pmol in the stated sample volume, ≈ 4.87 × 10¹⁰ copies/µL.

Calculation

  1. Approximate molecular weight

    M ≈ length × 617.96 g/mol per base pair + 36.04 g/mol

    M ≈ 1000 × 617.96 + 36.04

    M ≈ 617996 g/mol

  2. Molar concentration

    c = ρ / M

    c = 0.05 g/L / 617996 g/mol

    c ≈ 80.9067 nmol/L (nM)

  3. Amount in the sample

    n = c × V

    m = 1000 ng in 20 µL

    n ≈ 1.61813 pmol

  4. Copy number

    N = n × Nₐ, Nₐ = 6.02214076 × 10²³ mol⁻¹

    N/L = 8.09 × 10⁻⁸ mol/L × 6.02214076 × 10²³

    ≈ 4.87 × 10¹⁰ copies per µL

  5. Total copies in the sample

    N(total) = n(sample) × Nₐ

    N = 1.62 × 10⁻¹² mol × 6.02214076 × 10²³

    ≈ 9.74 × 10¹¹ molecules

Inputs

Nucleic acid
Double-stranded DNA
Length
1000 base pairs
Concentration
50 ng/µL
Volume
20 µL
MW per base pair
617.96 g/mol

Approximation: Average anhydrous MW per bp (sodium salt), + 36.04 g/mol for the 5′ terminal OH groups.

This is an average-composition estimate, not a sequence-exact molecular weight. Base composition, modifications, salt form and secondary structure all shift the true value — and the copy number inherits that same approximation.

Copy number uses N = n × Nₐ with Nₐ = 6.02214076 × 10²³ mol⁻¹, and counts whole molecules (for dsDNA, one double-stranded molecule such as a linear fragment or a plasmid of the stated length).

The constant used is shown above and can be overridden if your laboratory uses a different convention.

About this calculator

The molarity of a nucleic acid depends on its molecular weight, which in turn depends on its length. This calculator uses an average molecular weight per base or base pair, so the molecular weight it produces is an approximation, clearly labelled as such in every result.

The exact molecular weight of a specific sequence depends on its base composition, chemical modifications and salt form. LabReadyTools does not compute sequence-exact molecular weights. The constant used is shown on screen and can be overridden if your laboratory uses a different convention.

LabReadyTools is provided as a calculation aid. Users remain responsible for verifying calculations, units, chemical compatibility, experimental procedures and applicable safety requirements before laboratory use.

Related calculators

PCR setup

V(component) = C(final) × V(rxn) / C(stock)

Per-reaction PCR component volumes scaled to a run, with water to volume.

Open

Dilution

C1 × V1 = C2 × V2

Solve C1 × V1 = C2 × V2 for any missing variable.

Open

Molarity

n = m / M, c = n / V

Relate mass, amount of substance, molecular weight, volume and concentration.

Open