# Peptide Mass Calculator (Monoisotopic/Average)

Sums ProtParam residue masses for a peptide sequence (mono or average) and reports M, [M+H]⁺, [M+Na]⁺, [M+2H]²⁺. Educational use only.

> Canonical page: https://elysiatools.com/en/tools/peptide-mass-calculator

- **Category:** Education

- **Keywords:** peptide mass calculator, monoisotopic peptide mass, average peptide mass, residue mass summation, m plus h ion m/z, peptide molecular weight sequence, protparam residue masses, mass spectrometry peptide ion, singly doubly charged peptide, biochemistry calculator, lab calculator

## Overview

Calculate a peptide’s neutral mass from its amino acid sequence using monoisotopic or average ProtParam residue masses. The calculator returns M, [M+H]+, [M+Na]+, and [M+2H]2+ values for educational use and experimental planning.

## Inputs

- **Peptide Sequence** (text): Single-letter amino acid codes; 1–200 residues.
- **Mass Type** (select): Monoisotopic for short peptides in HRMS; average for longer chains.
- **Decimal Places** (number)

## When to use

- Estimate monoisotopic mass for short peptides analyzed by high-resolution mass spectrometry.
- Calculate average peptide mass for longer chains or general biochemical planning.
- Check expected protonated, sodiated, and doubly charged peptide ion values.

## How it works

- Enter a peptide sequence containing standard single-letter amino acid codes, from 1 to 200 residues.
- Choose Monoisotopic or Average mass mode.
- Set the number of decimal places from 0 to 8 if needed.
- Review the JSON result containing the peptide length, neutral mass, and calculated ion values.

## Use cases

- Compare theoretical peptide masses with expected mass spectrometry signals.
- Plan peptide synthesis and verify the approximate molecular weight of a sequence.
- Teach peptide residue mass summation, ion adducts, and charge states in biochemistry courses.

## Frequently asked questions

### What peptide sequences are supported?

Enter 1 to 200 standard amino acid residues using single-letter codes. Ambiguous codes such as B, J, O, U, X, and Z are rejected.

### What is the difference between monoisotopic and average mass?

Monoisotopic mass uses specific isotope masses and is commonly used for short peptides in high-resolution MS. Average mass reflects natural isotope abundance and is useful for longer chains.

### Which peptide ions does the calculator report?

It reports the neutral mass M and the m/z values for [M+H]+, [M+Na]+, and [M+2H]2+.

### Are spaces or separators allowed in a sequence?

Yes. Sequence input is case-insensitive, and spaces or separators are ignored.

### Can this calculator replace experimental measurements?

No. It provides theoretical mass estimates for education and experimental planning, not measured instrument results.

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