What it does
Before an organic reaction, chemists write a reagent table: every substance, its molar mass, how many equivalents are used relative to the limiting reagent, and what to weigh or measure. This tool builds that table and keeps the arithmetic right when you change the scale.
- Molar masses from formulas. Type the formula and the molar mass fills in, using IUPAC atomic weights. Brackets work, so Pd(P(C6H5)3)4 gives 1155.59. You can also type a molar mass directly.
- Equivalents set each reagent’s amount relative to the limiting reagent, which is 1 equivalent.
- Liquids with a density get a volume in µL or mL, for a syringe or pipette.
- Solutions with a molarity, such as n-butyllithium at 2.5 mol/L, get the volume of solution to add.
- Purity below 100 % scales up the mass to weigh, so a 95 % reagent still delivers the moles you planned.
- Scale by mmol, by the mass of any reagent, or by the volume of a liquid one: “I have 1.20 g of this, how much of everything else?”
- Yield: the theoretical yield of your product and the percent yield from what you isolated.
How to use it
- Press Example to see a filled-in table, or Start empty.
- For each reagent, type a name and formula (or molar mass), the equivalents, and a density, purity or molarity where they apply.
- Choose which reagent sets the scale and how much you have.
- Read the mass to weigh and the volume to measure for each row. Download the table as a PNG, PDF or Word file for your notebook.
- Type the product’s formula and the mass you isolated for the percent yield.
Worked example
A Suzuki coupling at 5.00 mmol scale: 4-bromoanisole (C7H7BrO, 187.04 g/mol, a liquid of density 1.494 g/mL) with 1.2 equivalents of phenylboronic acid, 2 equivalents of potassium carbonate and 5 mol % (0.05 equivalents) of Pd(PPh₃)₄.
- 4-Bromoanisole: 5.00 mmol = 935.2 mg, or 626 µL by syringe.
- Phenylboronic acid: 6.00 mmol × 121.93 = 731.6 mg.
- Potassium carbonate: 10.0 mmol × 138.20 = 1.382 g.
- Pd(PPh₃)₄: 0.250 mmol × 1155.59 = 288.9 mg.
The product, 4-methoxybiphenyl (C13H12O, 184.24 g/mol), has a theoretical yield of 921.2 mg. If you isolate 780 mg, that is 84.7 %.
Questions
What is an equivalent? The number of moles of a reagent for every mole of the limiting reagent. 1.2 equivalents means a 20 % excess. A catalyst at 5 mol % is 0.05 equivalents.
Should I use the purity for the limiting reagent too? Yes, if you know it. The tool divides the mass by the purity, so you weigh enough to get the moles you want.
Is my data saved? No. The table lives only on this page; download it to keep it. Nothing is sent anywhere.
Where the numbers come from
- Atomic weights: IUPAC/CIAAW standard atomic weights (abridged values).
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-08.