Skip to main content
Simple Calculators

Medical Unit Converter

Convert drug weights, volumes, body weight, temperature, and electrolyte mg ↔ mEq

Conversion

Clinical Disclaimer: This converter is a decision-support tool only. Electrolyte conversions use elemental ion equivalent weights — salt forms such as potassium chloride or calcium gluconate contain different mg amounts per mEq. Always verify conversions independently and follow your facility's protocols.

Related calculators

All health & fitness

Quick summary

Convert the units that come up in medication math: drug weights (mcg ↔ mg ↔ g), liquid volumes (mL ↔ tsp ↔ tbsp ↔ fl oz), body weight (lb ↔ kg for weight-based dosing), temperature (°C ↔ °F), and elemental electrolyte amounts (mg ↔ mEq for K⁺, Na⁺, Ca²⁺, Mg²⁺). Remember the metric ladder: 1 g = 1,000 mg = 1,000,000 mcg.

Reviewed by Simple Calculators TeamLast reviewed

For information only — not medical advice. Results are estimates from published formulas and can't account for your health history. Talk to a doctor or other qualified clinician before making health decisions.

How to use this calculator

  1. Enter the inputs requested by the calculator.
  2. Choose the units or options that match your situation and review the assumptions.
  3. Run or update the calculation to see the result.
  4. Review the result, breakdown, and formulas shown on the page.
  5. Check the inputs, units, dates, and limitations before saving or sharing the result.

Frequently asked questions

How do I convert mcg to mg?

Divide by 1,000. 500 mcg = 0.5 mg, and 250 mcg = 0.25 mg. Going the other way, multiply: 0.125 mg = 125 mcg. Micrograms and milligrams are the most commonly confused pair in medication errors, which is why "mcg" is preferred over the ambiguous "µg" in handwriting.

How many mL is a teaspoon?

One teaspoon is 5 mL, one tablespoon is 15 mL (3 tsp), and one fluid ounce is about 30 mL in clinical practice. Household spoons vary widely — for pediatric dosing, always use a marked oral syringe or dosing cup, never kitchen cutlery.

How do I convert mg to mEq?

Divide the mass in mg by the equivalent weight (atomic weight ÷ valence). For potassium: mEq = mg ÷ 39.1. For calcium (valence 2): mEq = mg ÷ 20.04. This converter handles potassium, sodium, calcium, and magnesium as elemental ions.

Why does 1 mEq of potassium chloride weigh more than 39.1 mg?

Because KCl includes chloride: 1 mEq of KCl weighs about 74.5 mg, of which 39.1 mg is elemental potassium. Supplement and IV labels usually state mEq of potassium, but if you see mg of a salt form, you must account for the salt, not just the ion.

Why convert lb to kg for dosing?

Almost all weight-based drug dosing is per kg (e.g., 15 mg/kg). Divide pounds by 2.2 to get kg — a 154 lb patient is 70 kg. Using pounds by mistake gives a 2.2× overdose, one of the classic medication errors.

Key terms

mEq (Milliequivalent)
A measure of an electrolyte's chemical activity: mg ÷ (atomic weight ÷ valence). Used for potassium, sodium, and other ions.
Equivalent Weight
Atomic weight divided by valence — the mg of an element per mEq. Potassium: 39.1, sodium: 23.0, calcium: 20.04, magnesium: 12.15.
Elemental vs Salt Form
Drug labels may state the ion (elemental) or the whole compound (salt). 600 mg of calcium carbonate contains only 240 mg elemental calcium.
Metric Ladder
kg → g → mg → mcg, each step ×1,000. Moving down multiplies; moving up divides.

Methodology, sources & limitations

This page shows the formula, assumptions, and limitations used for this estimate. Rates, thresholds, and other time-sensitive inputs can change, so verify them against the relevant official source before relying on a result.

For our review approach and the primary sources we consult, see the methodology and source policy. If you spot an outdated figure or formula, please contact us with a correction.