Concentration calculator
A mass and a volume, expressed every way concentration gets quoted. The interesting part is ppm, which contains an assumption about your solution that is almost never stated. Nothing you type here leaves your browser — it is worked out on your own device, so there is nothing to send and nothing to log.
ppm is not mg/L. It is mg/kg
Parts per million is a mass ratio: milligrams of solute per kilogram of solution. Milligrams per litre is a mass-to-volume ratio. They are the same number only when the solution weighs exactly one kilogram per litre.
For dilute solutions in water at room temperature that is close enough to true that the two get used interchangeably, and most people never learn there was an assumption. Then the solution is not dilute, or not water, and the two quantities part company:
| Pure water at 4 °C | 1.000 kg/L | ppm = mg/L exactly |
|---|---|---|
| Seawater | about 1.025 kg/L | 2.5% apart |
| Saturated brine | about 1.2 kg/L | 20% apart |
| Concentrated sulfuric acid | about 1.84 kg/L | 84% apart |
Leave the density box empty and this page assumes water and says so under the answer. Put a density in and it uses yours. What it will not do is quietly assume and stay quiet.
% w/v is not a percentage of anything
Percent weight in volume means grams per 100 millilitres. A 5% w/v solution is 5 g in 100 mL. That is a perfectly useful quantity and it is not a ratio of like to like — it is a mass over a volume with a percent sign on it, which means the number depends on the units in a way real percentages do not.
% w/w is a genuine ratio: grams per 100 grams of solution. It needs the density, which is why this page cannot give it to you honestly without one.
A note on the atomic weight table
This page does not use atomic weights — it works in whatever units you give it. It does load the site's table, because it shares a library with the molar mass tools, so the acknowledgement belongs here as well: the table is the abridged standard atomic weights 2024, © IUPAC / CIAAW, published at ciaaw.org and reproduced under their terms.