milliequivalent per liter
Molar concentrationexact by definition
The milliequivalent per litre is 10⁻³ eq/L, which is 1 mol/m³ of equivalents. It is the standard unit of water chemistry and clinical electrolytes: a water analysis is balanced by checking that cations in meq/L equal anions in meq/L, and serum sodium is reported as 140 mEq/L.
Watch out: Converting mg/L to meq/L means dividing by the equivalent weight, which is the molar mass over the charge. Calcium at 40.08 g/mol and charge 2 has an equivalent weight of 20.04, so 100 mg/L of calcium is 4.99 meq/L, not 2.5.
| 1 | 0.001 |
The unit exists to make charge balance checkable by eye. Concentrations in mg/L cannot be summed across ions of different charge and mass; in meq/L they can, and any analysis whose cation and anion sums differ by more than a few percent has an error in it.
One milliequivalent per liter in every molar concentration unit
| 1,000,000,000,000 | femtomole per liter (fM) | |
| 1,000,000,000 | picomole per liter (pM) | |
| 1,000,000 | nanomole per liter (nM) | |
| 1,000 | micromole per liter (μM) | |
| 1 | mole per cubic meter (mol/m³) | |
| 1 | millimole per liter (mM) | |
| 1 | milliequivalent per liter (meq/L)this unit | |
| 0.001 | mole per liter (molar) (M) | |
| 0.001 | mole per cubic decimeter (mol/dm³) | |
| 0.001 | normal (equivalent per liter) (N) |