RNA Molecular Weight Calculator

Calculate the molecular weight of any RNA sequence — mRNA, tRNA, rRNA, or synthetic oligos — in Daltons and g/mol with full nucleotide-level accuracy.

Chemical Formula

Try:

Molecular Weight

0.000 g/mol

Calculation Breakdown

Element	Atomic Mass	Atoms	Total	%

Total Molecular Weight

Elements in this compound

In formula

Other elements

Quick Examples

Click any compound to calculate its molecular weight instantly.

Water

H₂O

18.015 g/mol

Carbon Dioxide

CO₂

44.009 g/mol

Sodium Chloride

NaCl

58.443 g/mol

Glucose

C₆H₁₂O₆

180.156 g/mol

Ethanol

C₂H₅OH

46.069 g/mol

Sulfuric Acid

H₂SO₄

98.077 g/mol

How to Use the RNA Molecular Weight Calculator

To calculate the molecular weight of an RNA molecule, enter its nucleotide sequence or chemical formula into the input field and click "Calculate." The calculator computes the total mass from the ribonucleotide composition and strand length.

Follow these 4 steps to determine RNA molecular weight:

Enter the RNA sequence using single-letter codes (A, U, G, C) or type the full chemical formula of the RNA strand. Make sure to use U (uracil) instead of T (thymine) for RNA sequences.
Specify any terminal modifications if applicable. Unmodified RNA has a 5'-hydroxyl and 3'-hydroxyl by default. Phosphorylated 5' ends or 2',3'-cyclic phosphate termini change the total molecular weight.
Click "Calculate" or press Enter. The tool identifies each ribonucleotide (AMP, UMP, GMP, CMP), sums their residue weights, and corrects for phosphodiester bond water loss.
Read the result in Daltons (Da) or g/mol. Use the breakdown table to see each nucleotide type's mass contribution and percentage of total weight.

This tool is built for RNA researchers, molecular biologists designing siRNA or antisense oligonucleotides, and biochemists working with in vitro transcribed RNA for vaccine or gene therapy research.

How the RNA Molecular Weight Calculator Works

The RNA molecular weight calculator determines the mass of a polyribonucleotide chain by summing the molecular weights of individual ribonucleotide monophosphate residues. Each residue consists of a ribose sugar (with a 2'-hydroxyl group), a phosphate group, and one of four nitrogenous bases: adenine (A), uracil (U), guanine (G), or cytosine (C).

The calculation uses these residue weights and correction factors:

RNA MW Formula

MW = Σ(nᵢ × residue weightᵢ) - (N-1) × 18.02 + terminal group masses. N is total nucleotides; 18.02 Da is the mass of water lost per bond.

Ribonucleotide Residue Weights

AMP: 347.2 Da | UMP: 324.2 Da | GMP: 363.2 Da | CMP: 323.2 Da. These are internal residue weights after phosphodiester bond formation.

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Quick Estimate

MW(ssRNA) ≈ N × 340 Da, where N is the number of nucleotides. This approximation assumes roughly equal base composition.

RNA vs DNA Weight

RNA nucleotides are ~16 Da heavier than DNA nucleotides on average due to the 2'-hydroxyl group on ribose. A 1,000 nt ssRNA weighs ~340 kDa vs ~330 kDa for 1,000 nt ssDNA.

For a 21-nucleotide siRNA sense strand with the sequence AUGCGAUCCAGUACGUACGA-U, the calculator sums individual ribonucleotide weights: 5 × AMP + 4 × UMP + 5 × GMP + 7 × CMP, subtracts 20 water molecules for phosphodiester bonds, and adds the terminal hydroxyl masses. The result provides the exact mass needed for calculating transfection concentrations.

RNA molecular weight values are applied in quantitative real-time PCR (RT-qPCR) normalization, Northern blot band size estimation, mass spectrometry validation of synthetic RNA, and nanoparticle formulation for mRNA therapeutics.

Common Compound Molecular Weights

Reference table of frequently searched chemical compounds.

Chemical Formula	Compound Name	Molecular Weight
H₂O	Water	18.015 g/mol
CO₂	Carbon Dioxide	44.009 g/mol
NaCl	Sodium Chloride	58.443 g/mol
NH₃	Ammonia	17.031 g/mol
CH₄	Methane	16.043 g/mol
H₂SO₄	Sulfuric Acid	98.077 g/mol
CaCO₃	Calcium Carbonate	100.086 g/mol
C₆H₁₂O₆	Glucose	180.156 g/mol
C₂H₅OH	Ethanol	46.069 g/mol
HCl	Hydrochloric Acid	36.461 g/mol
NaOH	Sodium Hydroxide	39.997 g/mol
Ca(OH)₂	Calcium Hydroxide	74.092 g/mol
HNO₃	Nitric Acid	63.012 g/mol
KMnO₄	Potassium Permanganate	158.032 g/mol
CuSO₄	Copper(II) Sulfate	159.607 g/mol

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RNA Molecular Weight Calculator FAQs and Common Questions

Answers to common questions about calculating RNA molecular weight, nucleotide masses, and practical applications in molecular biology.

How is the molecular weight of an RNA strand calculated?

The molecular weight of a single-stranded RNA (ssRNA) is calculated by summing the molecular weights of each ribonucleotide monophosphate residue and adjusting for water molecules lost during phosphodiester bond formation. The formula is: MW = Σ(residue weights) - (N-1) × 18.02 + terminal group masses, where N is the number of nucleotides. Individual residue weights are AMP (347.2 Da), CMP (323.2 Da), GMP (363.2 Da), and UMP (324.2 Da).

What is the average molecular weight of a single RNA nucleotide?

The average molecular weight of a single RNA nucleotide residue is approximately 340 Da. This value is higher than the DNA average (~330 Da) because ribonucleotides contain a 2'-hydroxyl group on the ribose sugar that deoxyribonucleotides lack. The exact average depends on the base composition of the specific RNA sequence.

What is the key difference between RNA and DNA molecular weight calculations?

RNA molecular weight calculations differ from DNA in 3 ways. RNA uses ribose instead of deoxyribose, adding one oxygen atom (and one hydrogen) per nucleotide. RNA contains uracil (U) instead of thymine (T), with UMP weighing 324.2 Da compared to dTMP at 322.2 Da. RNA nucleotide residues are about 16 Da heavier on average than their DNA counterparts.

Can I calculate the molecular weight of mRNA, tRNA, or rRNA?

Yes. Enter the full nucleotide sequence of any RNA type — messenger RNA (mRNA), transfer RNA (tRNA), ribosomal RNA (rRNA), or small interfering RNA (siRNA). The calculation method is the same for all single-stranded RNA molecules: sum the individual ribonucleotide residue weights and adjust for polymerization water loss and terminal groups.

How do I convert RNA molecular weight to molar concentration?

To convert RNA mass to molar concentration: divide the mass in grams by the molecular weight in g/mol to get moles. For lab-scale quantities, the formula is: concentration (pmol/µL) = mass (ng/µL) × 1000 ÷ MW (Da). A 25-nucleotide RNA oligo with a molecular weight of approximately 8,000 Da at 100 ng/µL has a molar concentration of about 12.5 pmol/µL.

Does the 5' cap or poly-A tail affect RNA molecular weight?

Yes. A 5' m7G cap adds approximately 503 Da to the molecular weight. A poly-A tail adds roughly 329 Da per adenylate residue. For mRNA with a 200-nucleotide poly-A tail, the tail alone contributes about 65,800 Da. Accurate molecular weight calculation for mature mRNA requires including these post-transcriptional modifications.