Concentration - Solution Converter
Convert solution (mass) concentration between kg/L, g/L, mg/L, ppm, grains per gallon, pounds per gallon, pounds per million gallons and lb/ft³. Pick a source and a target unit, enter a value and read the result instantly.
Select two units to see the conversion factor.
Note on ppm: here ppm is treated as mg/L, which holds for dilute water-based solutions with a density near 1 kg/L. Percent by mass, mole-based units and other conversions that need density or molar mass are not included.
Solution Concentration Formula
Every unit on this page is a mass of dissolved substance per volume of solution, so each one is a fixed multiple of one reference unit, the gram per liter (g/L, which is the same as kg/m³). To convert, multiply the value by the size of the source unit in g/L, then divide by the size of the target unit in g/L. The conversions rest on exact definitions: 1 grain = 64.79891 mg, 1 pound = 0.45359237 kg, 1 US gallon = 3.785411784 L, 1 UK gallon = 4.54609 L and 1 ft³ = 28.316846592 L.
What Is Solution (Mass) Concentration?
Solution concentration expresses how much of a substance is dissolved in a given volume of solution. The units on this page are all mass concentrations: a mass of solute (kilograms, grams, milligrams, grains or pounds) divided by a volume of solution (liters, gallons or cubic feet). The SI form is the kilogram per cubic meter, which is numerically the same as the gram per liter (g/L).
Different fields use different members of this family. Chemistry and medicine use g/L and mg/L. Water quality reports use mg/L and, loosely, parts per million (ppm). In the United States, water hardness and treatment chemistry also use grains per gallon (gpg) and pounds per million gallons, and the grain is a very small mass of 64.79891 mg.
It is important to distinguish mass concentration from other ways of describing a solution. Percent by mass (w/w) compares the solute mass with the total solution mass, molarity counts moles per liter, and molality counts moles per kilogram of solvent. Converting between those and the units here requires the solution density or the molar mass, so they are deliberately not included and nothing is assumed on your behalf.
About ppm: parts per million is strictly a ratio, such as 1 mg of solute per 1 kg of solution. For dilute water-based solutions one liter weighs about one kilogram, so 1 ppm is taken as 1 mg/L, which is how the reference lists it and how water-quality results are normally reported. For concentrated solutions or liquids that are not close to water in density, ppm and mg/L differ and this equivalence should not be used.
Supported Units
This converter supports the following 11 solution concentration units. The last column shows how many grams per liter one unit equals. Remember that the US gallon (3.785 L) and the UK gallon (4.546 L) differ, so grains per gallon and pounds per gallon have separate US and UK versions.
| Unit | Symbol | Value in g/L |
|---|---|---|
| Kilogram per liter | kg/L | 1,000 |
| Gram per liter | g/L | 1 |
| Milligram per liter | mg/L | 0.001 |
| Part per million (ppm, taken as mg/L in water) | ppm | 0.001 |
| Grain per gallon (US) | gr/gal (US) | 0.01711806105 |
| Grain per gallon (UK) | gr/gal (UK) | 0.01425376752 |
| Pound per gallon (US) | lb/gal (US) | 119.8264273 |
| Pound per gallon (UK) | lb/gal (UK) | 99.77637266 |
| Pound per million gallon (US) | lb/Mgal (US) | 0.0001198264273 |
| Pound per million gallon (UK) | lb/Mgal (UK) | 9.977637266e-5 |
| Pound per cubic foot | lb/ft³ | 16.01846337 |
How to Use the Concentration - Solution Converter
- Type the concentration in the value box. Decimals and scientific notation such as 0.0025 or 2.5e-3 are accepted.
- Choose the From unit and the To unit.
- The result appears instantly, or press Convert Now. Very large or very small results are shown in scientific notation.
- Use Swap Units to reverse the conversion, Copy Result to copy the answer, open Show this value in all units for a full list, and Clear to start again.
Step-by-step by hand
- Find the size of each unit in the common base unit (g/L): 1 mg/L = 0.001 g/L and 1 gr/gal (US) = 0.01711806105 g/L.
- Divide the source size by the target size to get the conversion factor: 0.001 ÷ 0.01711806105 = 0.05841783116, so 1 mg/L = 0.05841783116 gr/gal (US).
- Multiply by your value: 250 mg/L × 0.05841783116 = 14.60445779 gr/gal (US).
Concentration cannot be negative, so only zero and positive numbers are accepted.
Common Concentration Conversions
- Water hardness: 120 mg/L equals 7.01013974 grains per US gallon.
- Softener setting: 10 gr/gal (US) equals 171.1806105 mg/L.
- Chemical dosing: 1 lb of chemical per million US gallons is 0.1198264273 mg/L.
- Laboratory stock: 0.25 g/L equals 250 mg/L and 0.00025 kg/L.
- Heavy liquid: 1.2 kg/L equals 1,200 g/L and 10.01448534 lb/gal (US).
- Imperial units: 1 lb/gal (UK) equals 99.77637266 g/L, while 1 lb/gal (US) equals 119.8264273 g/L.
- Per cubic foot: 1 lb/ft³ equals 16.01846337 g/L.
Milligram per Liter Conversion – Common Values
Quick reference for frequently used values
| mg/L | ppm (as mg/L) | g/L | gr/gal (US) | lb/Mgal (US) |
|---|---|---|---|---|
| 0.1 | 0.1 | 0.0001 | 0.005841783116 | 0.8345404452 |
| 1 | 1 | 0.001 | 0.05841783116 | 8.345404452 |
| 5 | 5 | 0.005 | 0.2920891558 | 41.72702226 |
| 10 | 10 | 0.01 | 0.5841783116 | 83.45404452 |
| 17.118 | 17.118 | 0.017118 | 0.9999964339 | 142.8566334 |
| 50 | 50 | 0.05 | 2.920891558 | 417.2702226 |
| 100 | 100 | 0.1 | 5.841783116 | 834.5404452 |
| 250 | 250 | 0.25 | 14.60445779 | 2,086.351113 |
| 500 | 500 | 0.5 | 29.20891558 | 4,172.702226 |
| 1,000 | 1,000 | 1 | 58.41783116 | 8,345.404452 |
Where and Why This Conversion Is Used
- Water treatment and testing: lab reports use mg/L while US test kits and softener manuals use grains per gallon.
- Municipal and industrial water plants: chemical feed rates are planned in pounds per million gallons and checked against mg/L targets.
- Aquariums, pools and hydroponics: nutrient and mineral levels are quoted in mg/L or ppm.
- Chemistry and pharmacy: stock solutions are prepared in g/L and diluted to mg/L.
- Environmental monitoring: pollutant and nutrient limits are written in mg/L, often compared with US lb/gal data.
- Industrial process control: brines, slurries and additive concentrations use kg/L, g/L or lb/gal.
For concentrations in moles per volume see the Concentration - Molar Converter. To change gallons and liters on their own use Liters to Gallons.