Concentration - Solution Converter
Convert between solution concentration units — mg/L, ppm, grains per gallon (water hardness), pounds per gallon, and more.
Results from this calculator are estimates provided for general informational purposes only, based on formulas, rates, and standards commonly accepted as of 2026. Figures may differ slightly from other calculators or professional sources due to rounding methods, differing assumptions, or regional regulations, and rules may change over time. Always consult a qualified professional — such as a financial advisor, healthcare provider, or other relevant specialist — before making decisions based on these results.
Result
100 mg/L = 100.11423 ppm
1 Milligram per Liter = 1.0011423 Parts per Million
1 Part per Million = 0.998859 Milligrams per Liter
100 mg/L in every supported unit
What is a Concentration - Solution Converter?
Solution concentration measures the MASS of solute dissolved per unit VOLUME of solution — a mass-basis figure, distinct from molar concentration, which counts moles of solute instead. It's the number behind "how hard is this water" (grains per gallon, ppm), "how much chlorine is in this treated water" (mg/L), or "how much active ingredient is in this liquid fertilizer" (pounds per gallon).
These units show up constantly in water quality and hardness testing, environmental monitoring of contaminants and discharge limits, and industrial process control, where operators dose chemicals by mass into a fixed volume of process water. Every unit here is defined relative to the base kilogram-per-liter unit by a fixed multiplier, letting a water utility's mg/L, a plumber's grains per gallon, and a plant engineer's pounds per cubic foot all be compared directly.
Conversion chart: Milligram per Liter to Parts per Million
Conversion table
| Milligram per Liter (mg/L) | Part per Million (ppm) |
|---|---|
| 0.01 mg/L | 0.010011423 ppm |
| 0.1 mg/L | 0.10011423 ppm |
| 1 mg/L | 1.0011423 ppm |
| 2 mg/L | 2.0022846 ppm |
| 3 mg/L | 3.0034269 ppm |
| 5 mg/L | 5.0057115 ppm |
| 10 mg/L | 10.011423 ppm |
| 20 mg/L | 20.022846 ppm |
| 50 mg/L | 50.057115 ppm |
| 100 mg/L | 100.11423 ppm |
| 1000 mg/L | 1001.1423 ppm |
Supported Units
| Unit | Symbol | In kg/L |
|---|---|---|
| Kilogram per Liter | kg/L | 1 kg/L |
| Gram per Liter | g/L | 0.001 kg/L |
| Milligram per Liter | mg/L | 1E-06 kg/L |
| Part per Million | ppm | 9.98859E-07 kg/L |
| Grain per Gallon (US) | gr/gal(US) | 1.71181E-05 kg/L |
| Grain per Gallon (UK) | gr/gal(UK) | 1.42538E-05 kg/L |
| Pound per Gallon (US) | lb/gal(US) | 0.11982643 kg/L |
| Pound per Gallon (UK) | lb/gal(UK) | 0.099776374 kg/L |
| Pound per Million Gallon (US) | lb/Mgal(US) | 1.19826E-07 kg/L |
| Pound per Cubic Foot | lb/ft³ | 0.016018463 kg/L |
About These Parameters
- Value
- The solution concentration value you want to convert, expressed in the "From" unit. Accepts decimals.
- From Unit
- The unit your input value is currently measured in — a water-quality report's mg/L, or a hardness test kit's grains per gallon.
- To Unit
- The unit you want the result converted into. Use the swap button to flip From and To instantly.
How Concentration - Solution Conversion Works
The Formula
Every unit here is defined by a fixed multiplier relative to kilograms per liter. To convert a value from one unit to another:
result = value × (factor of "From" unit ÷ factor of "To" unit)
For Milligram per Liter → Part per Million: multiply by 1.0011423. For example, 100 mg/L × 1.0011423 = 100.11423 ppm.
Solution Concentration vs. Molar Concentration
This page covers MASS-basis concentration — mass of solute per unit volume of solution, such as mg/L or lb/gal. The site's separate Concentration - Molar Converter covers MOLE-basis concentration (e.g. moles per liter, "molarity"), which counts particles of solute rather than their mass. Converting between the two requires knowing the solute's molar mass: dividing a mass-basis concentration by the molar mass gives the mole-basis concentration, and multiplying a mole-basis concentration by the molar mass gives the mass-basis figure back.
Understanding Water Hardness
Grains per gallon and parts per million (ppm) are the two units the water-treatment industry relies on to describe hardness — the concentration of dissolved calcium and magnesium minerals in water. One grain per gallon (US) equals roughly 17.1 mg/L (approximately 17.1 ppm on a mass basis), and water-softener systems are typically sized in "grains of capacity" against a measured grains-per-gallon hardness figure. Water below about 1 gr/gal is considered soft, while water above 10-15 gr/gal is considered very hard.
Example
A solution concentration of 100 mg/L equals 100.11423 ppm. For scale, US drinking-water standards generally set contaminant limits in the low single-digit mg/L range, while a moderately hard tap water might test around 7-10 grains per gallon (roughly 120-170 mg/L of hardness minerals).
Frequently Asked Questions
What does ppm mean in water testing?
In water testing, ppm (parts per million) is almost always used on a mass basis, meaning one milligram of solute per kilogram (roughly one liter) of water — which is why ppm and mg/L are treated as effectively interchangeable for dilute aqueous solutions, even though the two units are defined differently in principle.
What's a grain per gallon?
A grain per gallon (US) is a traditional water-hardness unit equal to one grain (1/7,000 of a pound) of dissolved mineral per US gallon of water, roughly 17.1 mg/L — it remains the standard unit on US water-softener sizing charts and hardness test strips even though most other concentration measurements have moved to metric mg/L.
How accurate are these conversions?
Every conversion factor used here is the standard, internationally recognized relationship between the underlying mass and volume units — results are limited only by floating-point display precision, not by rounded conversion constants.