Molarity to mass calculator
Concentration, volume and molecular weight in; how much to put on the balance out.
Free, no account needed. Nothing you type is sent anywhere or stored — the arithmetic runs in your browser.
Inputs
Results
Weigh out
292.2mg
- Same in grams
- 0.2922g
The arithmetic
Mass = concentration × volume × molecular weight. The only work is keeping the units straight, which is what the fields here do — mM against millilitres against g/mol lands on milligrams.
Use the molecular weight on your own bottle
This is the one that costs people an experiment. A hydrated salt weighs more than the anhydrous formula says, because the waters of crystallisation are part of what you are putting on the balance. Calcium chloride dihydrate is 147 g/mol against 111 for the anhydrous form — weigh out using the anhydrous figure and your solution is a quarter weak, with nothing to see in the tube.
Suppliers ship the same reagent in different hydration states, so the molecular weight on the bottle in your hand is the only one that is certainly right. Copy it from there rather than from a paper or a memory.
Weigh, then make up to volume
Dissolve the powder in less than the final volume and make it up to the mark afterwards. Adding the full volume of solvent to the powder gives you slightly more than you asked for, because the solid takes up room too.