Research Lab Tools Free lab calculators with the working shown All tools

Guides

How each calculation works

Each guide covers one calculation: the formula, a worked example, the usual mistakes and the references behind it. Each one links to the calculator that does the arithmetic.

  1. G-01

    How Peptide Molecular Weight Is Calculated

    Why a peptide weighs less than its amino acids added together, how residue masses work, when to use average or monoisotopic mass, and how terminal groups and disulfides change the result.

    3 min read T-01 · Tool
  2. G-02

    Amino Acid Properties Explained: Charge, pI, Hydropathy and A280

    What the sequence analyzer reports and how to read it: net charge at a given pH, isoelectric point, GRAVY hydropathy and the extinction coefficient at 280 nm, with the limits of each estimate.

    3 min read T-02 · Tool
  3. G-03

    Peptide Sequence Notation: One-Letter and Three-Letter Codes

    How peptide sequences are written: direction from N- to C-terminus, the 20 one- and three-letter codes, terminal groups like H- and -NH2, and the ambiguous codes that trip up calculators.

    2 min read T-03 · Tool
  4. G-04

    Moles and Molar Mass: Converting Between Grams and Moles

    The mole, Avogadro’s number and molar mass explained for bench work, with the conversion n = m / M worked through for peptide-scale quantities.

    2 min read T-04 · Tool
  5. G-05

    Molarity Explained, With Worked Examples

    What molar concentration means, how to rearrange m = c × V × M to find mass, volume or concentration, and the preparation details that keep a solution at the molarity you calculated.

    2 min read T-05 · Tool
  6. G-06

    The Dilution Equation (C1V1 = C2V2) and Serial Dilutions

    Why C1V1 = C2V2 works, how to solve it for any unknown, what “1:10” really means, and how to plan serial dilutions that stay accurate at small volumes.

    2 min read T-06 · Tool
  7. G-07

    Concentration Units Explained: M, mg/mL, % w/v and ppm

    How molar and mass-per-volume concentrations relate, why the molecular weight is the bridge between them, and what percentage and ppm really mean for a solution.

    2 min read T-07 · Tool
  8. G-08

    Metric Mass Prefixes: kg, g, mg, µg, ng and pg

    The metric mass prefixes, how to convert between them without factor-of-1000 slips, how to write micrograms unambiguously, and what your balance can actually weigh.

    2 min read T-08 · Tool
  9. G-09

    SI Units in the Laboratory: Volume, Amount, Concentration and Length

    The SI base and derived units behind everyday bench quantities, the accepted non-SI units such as the litre and ångström, and the formatting rules that keep values unambiguous.

    2 min read T-09 · Tool
  10. G-10

    Temperature Scales and Sample Storage

    Celsius, kelvin and Fahrenheit and how they relate, plus the temperature bands used for storing reagents and peptide samples, from room temperature to liquid nitrogen.

    2 min read T-10 · Tool
  11. G-11

    How to Prepare a Stock Solution

    A bench-level walk-through of stock solution preparation: choosing a concentration, correcting for purity and net peptide content, weighing, dissolving, making up to volume, and aliquoting.

    3 min read T-11 · Tool
  12. G-12

    Planning a Concentration Series

    How to space concentrations for an experiment (linear, 2-fold, half-log or 10-fold), when to dilute directly or serially, how to keep pipetting volumes accurate, and why the vehicle should stay constant.

    2 min read T-12 · Tool