🧪 peptide-calc — Peptide Research Calculators

Small, dependency-free JavaScript library for the everyday maths of preparing research-peptide solutions in the lab — reconstitution / dilution and molarity / concentration — plus a self-contained web calculator you can run in the browser.

▶️ Live calculator: https://paulnocturne.github.io/rsbiolabs-peptide-tools/

Maintained by RS Bio Labs · more tools at https://rsbiolabs.com/tools · background reading in the Knowledgebase.

⚠️ For in vitro research use only

This library performs standard laboratory arithmetic (concentration, dilution, molarity). It is not dosing software and provides no medical or veterinary guidance. Molecular weights should always be confirmed against your compound's Certificate of Analysis.

Install

npm install peptide-calc

Or drop src/peptide-calc.js straight into a page — it's a single ES module with zero dependencies.

Usage

import { reconstitution, molarity, MW } from 'peptide-calc';

// Reconstitution: 10 mg vial + 2 ml diluent, want to draw 250 mcg
reconstitution(10, 2, 250);
// → { mgPerMl: 5, mcgPerMl: 5000, drawMl: 0.05, units: 5 }
//   i.e. 5 mg/ml, draw 0.05 ml = 5 units on a U-100 syringe

// Molarity: 10 mg of retatrutide in 2 ml
molarity(10, 2, MW.retatrutide);
// → { molPerL: 0.001057, mM: 1.057, uM: 1056.8, mgPerMl: 5 }

API

| Function | Returns | |---|---| | concentration(mg, ml) | { mgPerMl, mcgPerMl } | | drawVolume(targetMcg, mcgPerMl) | ml to draw | | syringeUnits(ml, unitsPerMl = 100) | volume in syringe units (U-100 default) | | reconstitution(mg, ml, targetMcg, unitsPerMl = 100) | { mgPerMl, mcgPerMl, drawMl, units } | | molarity(massMg, volMl, mwGmol) | { molPerL, mM, uM, mgPerMl } | | MW | frozen table of approximate reference molecular weights (g/mol) |

All numeric inputs must be finite and > 0; invalid input throws a RangeError.

The maths

mg/ml     = mg ÷ ml
mcg/ml    = mg/ml × 1000
draw (ml) = target_mcg ÷ mcg/ml
units     = ml × unitsPerMl          (U-100 → ×100)
molarity  = mass_mg ÷ (MW_g/mol × volume_ml)   [mol/L]   ·   mM = ×1000 · µM = ×1e6

Develop

npm test        # runs the node:test suite (no dependencies)

Contributing

Issues and PRs welcome — especially additional verified molecular weights (with a source) and new lab-maths helpers. Please keep the library dependency-free.

License

MIT © RS Bio Labs. Built and maintained by the team at rsbiolabs.com — UK research peptides. Questions: [email protected].