Convert between milliequivalents (mEq) and milliliters (mL) for any electrolyte solution. Select a common stock solution or enter a custom concentration, then input any two of the three values (strength, mEq, mL) to solve for the third. Scroll below for electrolyte reference data, normal serum ranges, and common IV formulation concentrations.
| mEq to mL | mL to mEq |
|---|---|
| 5 mEq = 2.5 mL | 1 mL = 2 mEq |
| 10 mEq = 5 mL | 2 mL = 4 mEq |
| 15 mEq = 7.5 mL | 3 mL = 6 mEq |
| 20 mEq = 10 mL | 4 mL = 8 mEq |
| 25 mEq = 12.5 mL | 5 mL = 10 mEq |
| 30 mEq = 15 mL | 7 mL = 14 mEq |
| 40 mEq = 20 mL | 10 mL = 20 mEq |
| 50 mEq = 25 mL | 12 mL = 24 mEq |
| 60 mEq = 30 mL | 15 mL = 30 mEq |
| 80 mEq = 40 mL | 25 mL = 50 mEq |
| mL = mEq / (mEq/mL) and mEq = (mEq/mL) x mL. Strength = 2 mEq/mL. | |
| mEq to mL | mL to mEq |
|---|---|
| 10 mEq = 10 mL | 1 mL = 1 mEq |
| 25 mEq = 25 mL | 2 mL = 2 mEq |
| 50 mEq = 50 mL | 5 mL = 5 mEq |
| 75 mEq = 75 mL | 10 mL = 10 mEq |
| 100 mEq = 100 mL | 20 mL = 20 mEq |
| 150 mEq = 150 mL | 30 mL = 30 mEq |
| 200 mEq = 200 mL | 50 mL = 50 mEq |
| 250 mEq = 250 mL | 60 mL = 60 mEq |
| 300 mEq = 300 mL | 100 mL = 100 mEq |
| 500 mEq = 500 mL | 200 mL = 200 mEq |
| mL = mEq / (mEq/mL) and mEq = (mEq/mL) x mL. Strength = 1 mEq/mL. | |
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Meq to mL Formulas
Two forms of the conversion are common depending on how the concentration is expressed.
When concentration is in mEq/mL (typical on vial labels):
mL = mEq / (mEq/mL)
When concentration is in mEq/L (typical in lab reports):
mL = (mEq / C) x 1000
Variables:
- mL = volume of solution in milliliters
- mEq = milliequivalents of the solute (the amount of ionic charge)
- mEq/mL = concentration as printed on the product label
- C = concentration in mEq/L (divide by 1000 to get mEq/mL)
The calculator above uses the mEq/mL form directly, which matches how injectable electrolyte products are labeled in the United States.
What Is a Milliequivalent (mEq)?
A milliequivalent is one-thousandth of a chemical equivalent. Unlike milligrams, which measure mass alone, milliequivalents account for both the mass and the ionic charge (valence) of a substance. This makes mEq the preferred unit for electrolytes in clinical medicine because body fluid balance depends on charge, not weight.
The relationship between milligrams and milliequivalents is:
mEq = (mg x valence) / molecular weight
For monovalent ions (valence = 1) such as Na+, K+, and Cl-, one milliequivalent equals one millimole. For divalent ions (valence = 2) such as Ca2+ and Mg2+, one millimole equals two milliequivalents. This distinction matters when converting between lab values reported in mmol/L (common outside the US) and mEq/L (standard in the US).
Electrolyte Reference Data
The table below lists the molecular weight, ionic valence, and weight per milliequivalent for electrolytes commonly encountered in pharmacy and clinical practice. Use these values with the calculator above when working with a custom solution.
| Substance | Formula | MW (g/mol) | Valence | mg per 1 mEq |
|---|---|---|---|---|
| Sodium chloride | NaCl | 58.44 | 1 | 58.44 |
| Potassium chloride | KCl | 74.55 | 1 | 74.55 |
| Sodium bicarbonate | NaHCO3 | 84.01 | 1 | 84.01 |
| Calcium chloride (dihydrate) | CaCl2 2H2O | 147.01 | 2 | 73.51 |
| Calcium gluconate | C12H22CaO14 | 430.37 | 2 | 215.19 |
| Magnesium sulfate (heptahydrate) | MgSO4 7H2O | 246.47 | 2 | 123.24 |
| Potassium phosphate (dibasic) | K2HPO4 | 174.18 | 1 (per K+) | 174.18 |
| Sodium acetate (trihydrate) | CH3COONa 3H2O | 136.08 | 1 | 136.08 |
| Sodium phosphate (dibasic) | Na2HPO4 7H2O | 268.07 | 1 (per Na+) | 268.07 |
| Potassium acetate | CH3COOK | 98.14 | 1 | 98.14 |
Normal Serum Electrolyte Ranges
When calculating replacement doses, the target is to restore serum levels to the normal range. The reference ranges below are for healthy adults; pediatric and critically ill patients may have narrower targets.
| Electrolyte | Normal Range (mEq/L) | Equivalent (mmol/L) |
|---|---|---|
| Sodium (Na+) | 136 to 145 | 136 to 145 |
| Potassium (K+) | 3.5 to 5.0 | 3.5 to 5.0 |
| Chloride (Cl-) | 98 to 106 | 98 to 106 |
| Bicarbonate (HCO3-) | 22 to 28 | 22 to 28 |
| Calcium (Ca2+, ionized) | 2.2 to 2.6 | 1.1 to 1.3 |
| Magnesium (Mg2+) | 1.3 to 2.1 | 0.65 to 1.05 |
| Phosphate (PO4 3-) | 1.8 to 2.6 | 0.81 to 1.45 |
For monovalent ions the mEq/L and mmol/L columns are identical. For divalent ions, mEq/L = mmol/L x 2. Labs in the United States typically report sodium, potassium, chloride, and bicarbonate in mEq/L; calcium and magnesium may appear in either mg/dL or mmol/L depending on the institution.
Common Injectable Electrolyte Concentrations
The following table lists stock concentrations for injectable electrolyte products frequently used in US hospitals. These are the values pre-loaded in the calculator’s dropdown menu.
| Product | Label Strength | Primary Ion | Approx. mEq/mL |
|---|---|---|---|
| KCl injection | 2 mEq/mL | K+ | 2 |
| NaHCO3 8.4% | 84 mg/mL | Na+ | 1 |
| NaCl 23.4% | 234 mg/mL | Na+ | 4 |
| Calcium gluconate 10% | 100 mg/mL | Ca2+ | 0.465 |
| CaCl2 10% | 100 mg/mL | Ca2+ | 1.36 |
| MgSO4 50% | 500 mg/mL | Mg2+ | 4 |
| KCl injection (dilute) | 0.1 mEq/mL | K+ | 0.1 |
| NaCl 0.9% (Normal Saline) | 9 mg/mL | Na+ | 0.154 |
| Lactated Ringer’s | mixed | Na+ | 0.130 (Na+) |
| Values are approximate. Always verify the concentration on the actual product label before dosing. | |||
How to Convert mEq to mL (Step by Step)
The steps below walk through a real clinical scenario: preparing a potassium chloride dose from a 2 mEq/mL vial.
- Identify the ordered dose: 40 mEq of KCl.
- Read the vial label for the concentration: 2 mEq/mL.
- Apply the formula: mL = mEq / (mEq/mL) = 40 / 2 = 20 mL.
- Draw up 20 mL from the vial to obtain the ordered 40 mEq dose.
- Verify using the calculator above by entering Strength = 2, Amount = 40, then pressing Calculate to confirm Volume = 20 mL.
Example: Sodium Bicarbonate Dose
A physician orders 50 mEq of sodium bicarbonate. The available product is NaHCO3 8.4%, which provides approximately 1 mEq/mL.
mL = 50 mEq / 1 mEq/mL = 50 mL
You would draw 50 mL of the 8.4% sodium bicarbonate solution. To double-check: the 8.4% label means 84 mg/mL. The molecular weight of NaHCO3 is 84.01 g/mol with a valence of 1, so 84 mg / 84.01 mg/mmol x 1 = ~1 mEq/mL, confirming the concentration.
Why Electrolytes Use mEq Instead of mg
Milligrams measure mass. Milliequivalents measure the number of ionic charges in solution. Body fluids maintain electrical neutrality: the total positive charges (cations) must equal the total negative charges (anions). Because different ions have different masses per charge (74.55 mg of K+ and 23 mg of Na+ each supply 1 mEq), milligrams alone cannot predict physiologic effect. Ordering and reporting in mEq ensures that replacement doses restore the correct charge balance, regardless of which salt form is used.
As a practical example, 40 mEq of potassium can be delivered as 2,982 mg of KCl (MW 74.55, valence 1) or as 3,918 mg of potassium gluconate (MW 234.25, valence 1). Both deliver the same ionic activity despite weighing different amounts.
