Bench calculators for peptide & solution work
Free calculators for molecular weight, molarity, dilutions and units. Every tool shows its formula, a worked example and the sources behind it, so you can check the numbers before you trust them.
The toolbox
Results update as you type, and the formula is shown with your own numbers.
Molecular weight, composition and notation for amino-acid sequences.
3 toolsAverage and monoisotopic molecular weight plus molecular formula for any peptide sequence, with terminal modifications and disulfide bonds.
Composition, net charge at any pH, isoelectric point, GRAVY hydropathy and extinction coefficient for a peptide sequence.
Count residues and peptide bonds, and convert a sequence between one-letter and three-letter amino-acid codes.
Move between grams, moles and molarity using molar mass.
2 toolsConvert between mass and amount of substance (moles) using molecular weight, and see the number of molecules.
Solve for mass, volume or molar concentration from the other two values and the molecular weight.
Plan stock solutions, dilutions and concentration series at the bench.
4 toolsSolve C1V1 = C2V2 for any one value, or plan a serial dilution with transfer and diluent volumes for each step.
Convert between molar units (M, mM, µM, nM) and mass-per-volume units (mg/mL, µg/mL, % w/v, ppm) using molecular weight.
Mass to weigh for a stock solution, or solvent volume for a weighed amount, with purity correction and aliquot planning.
Build a printable worksheet of stock and diluent volumes for a list or series of target concentrations.
Mass, volume, amount, concentration and temperature units.
3 toolsConvert between kilograms, grams, milligrams, micrograms, nanograms and picograms without factor-of-1000 slips.
Convert volume, amount of substance, molar concentration, mass concentration and length units used at the bench.
Convert between Celsius, Fahrenheit and kelvin, with presets for common laboratory storage temperatures.
Built to be checked
Each result lists the equation and the working, so a misplaced unit is easy to spot before it reaches the bench.
Atomic weights, residue formulas, pKa values and extinction coefficients are taken from IUPAC, NIST and the original papers, and cited on every page.
Copy a link that reopens your exact inputs, cite a tool in a methods section, or embed it on a lab wiki or course page.
Guides
Short explanations with worked examples, common mistakes and references. Useful for teaching, too.
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.
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.
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.
The mole, Avogadro’s number and molar mass explained for bench work, with the conversion n = m / M worked through for peptide-scale quantities.
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.
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.
For lab wikis, courses and core facilities
Every tool has a copy-and-paste embed code. It is free to use, needs no account and loads no tracking scripts.