Tools / Laboratory
Laboratory converter.
Quick calculations for mass, moles, concentration and dilution. The tool is intended for laboratory calculations, not for dosing in humans.
Features
- — calculation in the browser
- — no data storage
- — SI units and clear formulas
- — no doses for humans
Formulas
What is calculated.
All input values are converted to consistent units (mg, g, mL, L, g/mol) before calculation. Results are shown to five significant figures; for traceability, always record the input values and the molar mass used.
Mass and moles
n (mol) = m (g) / M (g/mol)
If the mass is in mg, convert it to g before dividing. The result is the amount of substance in moles.
Concentration
c (mol/L) = (m (g) / M (g/mol)) / V (L)
Mass concentration is m / V. Molar concentration links mass, molar mass and volume.
Dilution
C1 × V1 = C2 × V2
The equation holds if C1 and C2 are in the same unit and V1 and V2 are in the same unit. When preparing a final volume, the solvent added equals V2 − V1.
Examples
The examples use a fictitious molar mass of 1000 g/mol to keep the calculation clear. For your peptide, enter the molar mass of the exact form.
1. Mass to moles
5 mg of a substance with a molar mass of 1000 g/mol: 5 mg = 0.005 g; 0.005 / 1000 = 0.000005 mol, which is 5 µmol.
2. Concentration
5 mg in 2 mL: the mass concentration is 2.5 mg/mL. The molar concentration is 5 / (1000 × 2) = 0.0025 mol/L, which is 2.5 mM.
3. Dilution
From a 10 mM stock you want 1 mM in 1 mL. V1 = (1 × 1) / 10 = 0.1 mL = 100 µL of stock; add 0.9 mL = 900 µL of solvent to a final volume of 1 mL.
Common mistakes
- Mixing units. mg, g, mL and L are not interchangeable; convert them before calculating.
- Wrong molar mass. Free base, acetate, trifluoroacetate and hydrate have different masses.
- Added volume is not final volume. If you add 9 mL of solvent to 1 mL of stock, the final volume is approximately 10 mL, not 9 mL.
- Volumes are not always additive. For precise solutions, use a volumetric flask.
- Purity is not mass fraction. HPLC purity and peptide content are not the same quantity.
- Temperature. Volume changes with temperature; account for temperature in critical measurements.
Tool limitations
The tool is informational and intended for laboratory calculations. It does not provide dosing instructions, does not account for pharmacokinetics and does not replace a validated laboratory procedure. For human use, consult a qualified professional and follow applicable legislation.
To understand analytical data, read HPLC and mass spectrometry , How to read a certificate of analysis and the Peptide glossary. For storage and reconstitution, the relevant article is Storage and reconstitution of peptides.