What is a milliequivalent (mEq)?

A milliequivalent is 1/1000 of an equivalent, the amount of an ion that carries one millimole of charge. For monovalent ions (Na+, K+, Cl-) 1 mmol = 1 mEq; for divalent ions (Ca2+, Mg2+) 1 mmol = 2 mEq.

How do I convert mg to mEq?

mEq = mg ÷ formula weight × valence. For the ion itself use the ion's weight: 23 mg of sodium (22.99 g/mol, valence 1) = 1 mEq, and 20 mg of calcium (40.08 g/mol, valence 2) = 1 mEq. For a salt use the salt's formula weight and its total cation charge per formula unit.

How many mEq are in 1 gram of potassium chloride?

About 13.4 mEq. KCl weighs 74.55 g/mol and releases one K+ per formula unit, so 1000 mg ÷ 74.55 × 1 = 13.41 mEq of potassium (and 13.41 mEq of chloride). 20 mEq of KCl is therefore 1.49 g of the salt, and 40 mEq is 2.98 g.

How many mEq of calcium are in calcium gluconate and calcium chloride?

1 g of calcium chloride dihydrate (147.01 g/mol) contains 13.6 mEq (272.6 mg) of calcium. 1 g of calcium gluconate contains about 4.65 mEq (93 mg) of calcium on the anhydrous basis used on injection labels (430.37 g/mol), or 4.46 mEq (89.4 mg) if calculated from the monohydrate (448.39 g/mol). Calcium chloride delivers about three times as much calcium per gram.

How do I convert mg/dL to mEq/L?

mEq/L = mg/dL × 10 ÷ formula weight × valence. A serum calcium of 10 mg/dL is 10 × 10 ÷ 40.08 = 2.50 mmol/L, which is 4.99 mEq/L because calcium is divalent. Magnesium 2.0 mg/dL is 0.82 mmol/L or 1.65 mEq/L.

What is the difference between mmol and mEq?

mmol counts particles; mEq counts charge. For monovalent ions mEq = mmol, for divalent ions mEq = 2 × mmol, so 12 mmol of magnesium is 24 mEq.

How many mEq of lithium are in 300 mg of lithium carbonate?

8.12 mEq. Lithium carbonate (Li2CO3, 73.89 g/mol) releases two Li+ ions per formula unit, so 300 ÷ 73.89 × 2 = 8.12 mEq of lithium.

Why does phosphate have more than one valence?

Phosphate exists as H2PO4- (valence 1) and HPO4 2- (valence 2); at pH 7.4 the mix averages about 1.8 mEq per mmol. Labs report phosphorus as mg/dL of elemental P (30.97 g/mol), so the "Phosphorus as P" option uses 1.8. Phosphate is usually prescribed in mmol to avoid this ambiguity.

What is the displayed ideal ion mOsm?

A particle count for the selected ion alone: 1 mmol of that ion is shown as about 1 mOsm. It is not total solution osmolarity because it excludes counterions, other solutes and non-ideal behavior.

Is this a morphine milligram equivalent (MME) calculator?

No. Chemical milliequivalents measure ionic charge. Morphine milligram equivalents (MME) are an opioid-dose concept and must not be calculated with this tool.

Milliequivalent Calculator

Convert mg, mmol and mEq for an ion or for a salt such as KCl, CaCl2 or MgSO4, and convert lab concentrations between mg/dL, mmol/L and mEq/L, with every step shown.

mEq = mg ÷ formula weight × valence.

Electrolyte chemistry only. This is not an opioid Morphine Milligram Equivalent (MME) calculator and not a dosing tool. In the ion converter, mg means the mass of the ion itself; use the salt converter below for the mass of a compound such as KCl or calcium gluconate.

Ion converter

Electrolyte / Ion

Input unit

Amount

Amount of the selected ion—not a compound, salt, or concentration.

Results

mEq

—

mmol

—

Ideal ion mOsm*

—

Salt converter: mg of KCl, CaCl2, MgSO4… to mEq

Uses the formula weight of the whole compound (hydrate water included) and the cations it releases: mEq = mg ÷ FW × cations per formula unit × charge.

Compound

Amount

Unit

mEq of cation

—

mg of salt

—

mmol of salt

—

Elemental cation

—

Choose a compound and enter an amount.

Lab concentration: mg/dL ⇄ mmol/L ⇄ mEq/L

mmol/L = mg/dL × 10 ÷ formula weight; mEq/L = mmol/L × valence.

Ion

Value

Unit

mg/dL

—

mg/L

—

mmol/L

—

mEq/L

—

Choose an ion and enter a lab value.

Formula, worked examples and scope

mEq = mmol × |charge|, mmol = mg ÷ formula weight. For a salt, the charge is the total cation charge per formula unit: Li2CO3 gives 2 × 1 = 2 mEq per mmol, calcium citrate Ca3(C6H5O7)2 gives 3 × 2 = 6.

40 mEq of KCl: 40 ÷ 1 = 40 mmol × 74.55 = 2,982 mg (about 3 g) of potassium chloride, containing 1,564 mg of potassium.
650 mg sodium bicarbonate tablet: 650 ÷ 84.01 × 1 = 7.74 mEq of sodium and of bicarbonate.
4 g magnesium sulfate heptahydrate: 4000 ÷ 246.47 × 2 = 32.5 mEq (394 mg) of magnesium.
Sodium 140 mEq/L: 140 mmol/L × 22.99 ÷ 10 = 322 mg/dL.

*mOsm limitation: the ion converter's mOsm treats one mmol of the selected free ion as one ideal mOsm. It excludes counterions, other solutes and osmotic coefficients, so it is not total solution osmolarity.

For education and independent arithmetic checking only. Check product labels, which state mEq per tablet or per mL, and do not use this page alone to prepare, prescribe or administer medication.

Formula weights from NIST standard atomic weights; unit conventions per the Merck Manual conversion tables.

mEq per gram of common salts

Compound	FW (g/mol)	mEq per g	mg salt per mEq	Elemental cation
Potassium chloride KCl	74.55	13.41	74.6	52.4 % Potassium
Potassium bicarbonate KHCO3	100.12	9.99	100.1	39.1 % Potassium
Potassium acetate CH3COOK	98.14	10.19	98.1	39.8 % Potassium
Potassium citrate monohydrate K3C6H5O7·H2O	324.41	9.25	108.1	36.2 % Potassium
Potassium gluconate C6H11KO7	234.25	4.27	234.2	16.7 % Potassium
Sodium chloride NaCl	58.44	17.11	58.4	39.3 % Sodium
Sodium bicarbonate NaHCO3	84.01	11.90	84.0	27.4 % Sodium
Sodium acetate (anhydrous) CH3COONa	82.03	12.19	82.0	28.0 % Sodium
Sodium citrate dihydrate Na3C6H5O7·2H2O	294.10	10.20	98.0	23.5 % Sodium
Calcium chloride dihydrate CaCl2·2H2O	147.01	13.60	73.5	27.3 % Calcium
Calcium gluconate (anhydrous basis, as labeled) C12H22CaO14	430.37	4.65	215.2	9.3 % Calcium
Calcium gluconate monohydrate C12H22CaO14·H2O	448.39	4.46	224.2	8.9 % Calcium
Calcium carbonate CaCO3	100.09	19.98	50.0	40.0 % Calcium
Calcium citrate tetrahydrate Ca3(C6H5O7)2·4H2O	570.49	10.52	95.1	21.1 % Calcium
Magnesium sulfate heptahydrate MgSO4·7H2O	246.47	8.11	123.2	9.9 % Magnesium
Magnesium chloride hexahydrate MgCl2·6H2O	203.30	9.84	101.7	12.0 % Magnesium
Magnesium oxide MgO	40.30	49.62	20.2	60.3 % Magnesium
Ammonium chloride NH4Cl	53.49	18.69	53.5	33.7 % Ammonium
Lithium carbonate Li2CO3	73.89	27.07	36.9	18.8 % Lithium

Calcium gluconate injection labels state about 93 mg (4.65 mEq) of calcium per gram, the anhydrous basis; the monohydrate gives 89.4 mg (4.46 mEq).

Quick reference — common ions (per 1 mEq)

Ion	Formula wt (g/mol)	Valence	mg per 1 mEq	mmol per 1 mEq
Sodium (Na+)	22.9898	1	22.99	1
Potassium (K+)	39.0983	1	39.098	1
Calcium (Ca2+)	40.078	2	20.039	0.5
Magnesium (Mg2+)	24.305	2	12.153	0.5
Chloride (Cl-)	35.45	1	35.45	1
Bicarbonate (HCO3-)	61.0168	1	61.017	1
Phosphate mono (H2PO4-)	96.9872	1	96.987	1
Phosphate di (HPO4 2-)	95.9793	2	47.99	0.5
Phosphorus as P (lab value, pH 7.4)	30.9738	1.8	17.208	0.5556
Ammonium (NH4+)	18.0385	1	18.039	1
Lithium (Li+)	6.94	1	6.94	1

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Quick answer

mEq = mg ÷ formula weight × valence. For a salt, use the salt's formula weight and its total cation charge: 1 g of potassium chloride (KCl, 74.55 g/mol) is 1000 ÷ 74.55 = 13.4 mEq of K+, and 1 g of calcium chloride dihydrate (147.01 g/mol, Ca2+) is 1000 ÷ 147.01 × 2 = 13.6 mEq of Ca2+.

Examples

Amount	mEq	Working
1 g KCl	13.4 mEq K+	1000 ÷ 74.55 × 1
1 g NaCl	17.1 mEq Na+	1000 ÷ 58.44 × 1
1 g MgSO4·7H2O	8.11 mEq Mg2+	1000 ÷ 246.47 × 2
300 mg Li2CO3	8.12 mEq Li+	300 ÷ 73.89 × 2
Calcium 10 mg/dL	4.99 mEq/L	10 × 10 ÷ 40.08 × 2

Pick an ion or a salt, type mg, mmol or mEq, and copy any result with the working shown.

Summary

The milliequivalent calculator applies charge-based stoichiometry: mEq = mmol × valence and mmol = mg ÷ formula weight. It has three parts: an ion converter (mass of the ion itself), a salt converter that uses the formula weight of the whole compound and the number of cations it releases (KCl, NaCl, NaHCO3, calcium chloride and gluconate, magnesium sulfate, lithium carbonate and more), and a lab concentration converter between mg/dL, mg/L, mmol/L and mEq/L. The ion mOsm figure is an idealized count for that ion only, not total solution osmolarity.

How it works

Ion converter: pick the ion, choose mEq, mmol, mg or mOsm and type the amount of the ion itself.
Salt converter: pick the compound (hydrate stated), enter mg, g, mmol or mEq of the salt; the tool uses the salt formula weight and its cations per formula unit × charge.
Concentration converter: pick the ion and enter a lab value in mg/dL, mg/L, mmol/L or mEq/L; mmol/L = mg/dL × 10 ÷ formula weight.
Every result shows the arithmetic, and the copy buttons copy the displayed value.

Use cases

Check how many mEq of potassium are in a gram of KCl, potassium citrate or potassium bicarbonate.
Work out elemental calcium or magnesium in a salt, for example calcium carbonate (40 %) or magnesium sulfate heptahydrate (9.9 %).
Convert a lab calcium, magnesium or sodium value between mg/dL, mmol/L and mEq/L.
Compare monovalent and divalent ion conversions when studying pharmacy calculations.
Cross-check stoichiometric arithmetic against a product label or textbook value.

Frequently Asked Questions

Last updated: 2026-10-09 · Reviewed by Nham Vu