Ionized calcium conversion: to convert ionized calcium from mg/dL to mmol/L, divide by 4.008 (or multiply by 0.2495). To convert mmol/L to mg/dL, multiply by 4.008. Example: ionized calcium 4.8 mg/dL = 1.20 mmol/L. Total calcium uses the same factor.
Ionized Calcium (Ca²⁺) Calculator
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Calcium Unit Conversion Factors (Ionized and Total Calcium)
Calcium (Ca) has an atomic mass of 40.08 and a charge of +2. The same factors apply to ionized calcium (iCa, free calcium) and total serum calcium.
| Convert calcium | Formula | Example |
|---|---|---|
| mg/dL to mmol/L | mmol/L = mg/dL ÷ 4.008 (or × 0.2495) | 8.5 mg/dL = 2.12 mmol/L |
| mmol/L to mg/dL | mg/dL = mmol/L × 4.008 | 1.2 mmol/L = 4.81 mg/dL |
| mg/L to mmol/L | mmol/L = mg/L ÷ 40.08 | 100 mg/L = 2.50 mmol/L |
| mmol/L to mEq/L | mEq/L = mmol/L × 2 | 1.2 mmol/L = 2.4 mEq/L |
| mg/dL to mEq/L | mEq/L = mg/dL ÷ 2.004 | 10 mg/dL = 4.99 mEq/L |
| mmol to mg (amount) | mg = mmol × 40.08 | 15 mmol = 601 mg |
Ionized Calcium mg/dL to mmol/L Chart
| Ionized calcium (mg/dL) | Ionized calcium (mmol/L) | Ionized calcium (mEq/L) |
|---|---|---|
| 3.0 mg/dL | 0.75 mmol/L | 1.50 mEq/L |
| 3.5 mg/dL | 0.87 mmol/L | 1.75 mEq/L |
| 3.8 mg/dL | 0.95 mmol/L | 1.90 mEq/L |
| 4.0 mg/dL | 1.00 mmol/L | 2.00 mEq/L |
| 4.2 mg/dL | 1.05 mmol/L | 2.10 mEq/L |
| 4.4 mg/dL | 1.10 mmol/L | 2.20 mEq/L |
| 4.5 mg/dL | 1.12 mmol/L | 2.25 mEq/L |
| 4.6 mg/dL | 1.15 mmol/L | 2.30 mEq/L |
| 4.8 mg/dL | 1.20 mmol/L | 2.40 mEq/L |
| 5.0 mg/dL | 1.25 mmol/L | 2.50 mEq/L |
| 5.2 mg/dL | 1.30 mmol/L | 2.59 mEq/L |
| 5.3 mg/dL | 1.32 mmol/L | 2.64 mEq/L |
| 5.4 mg/dL | 1.35 mmol/L | 2.69 mEq/L |
| 5.6 mg/dL | 1.40 mmol/L | 2.79 mEq/L |
| 5.8 mg/dL | 1.45 mmol/L | 2.89 mEq/L |
| 6.0 mg/dL | 1.50 mmol/L | 2.99 mEq/L |
| 6.5 mg/dL | 1.62 mmol/L | 3.24 mEq/L |
| 7.0 mg/dL | 1.75 mmol/L | 3.49 mEq/L |
Ionized Calcium mmol/L to mg/dL Chart
To convert ionized calcium from mmol/L to mg/dL, multiply by 4.008. You can also use the ionized calcium mmol/L to mg/dL converter.
| Ionized calcium (mmol/L) | Ionized calcium (mg/dL) |
|---|---|
| 0.80 mmol/L | 3.21 mg/dL |
| 0.90 mmol/L | 3.61 mg/dL |
| 1.00 mmol/L | 4.01 mg/dL |
| 1.05 mmol/L | 4.21 mg/dL |
| 1.10 mmol/L | 4.41 mg/dL |
| 1.12 mmol/L | 4.49 mg/dL |
| 1.15 mmol/L | 4.61 mg/dL |
| 1.20 mmol/L | 4.81 mg/dL |
| 1.25 mmol/L | 5.01 mg/dL |
| 1.30 mmol/L | 5.21 mg/dL |
| 1.32 mmol/L | 5.29 mg/dL |
| 1.40 mmol/L | 5.61 mg/dL |
| 1.50 mmol/L | 6.01 mg/dL |
| 1.60 mmol/L | 6.41 mg/dL |
Total Calcium mg/dL to mmol/L Chart
Total (serum) calcium converts with the same factor. Values are about twice as high as ionized calcium. Dedicated tools: calcium mg/dL to mmol/L and calcium mmol/L to mg/dL.
| Total calcium (mg/dL) | Total calcium (mmol/L) |
|---|---|
| 6.0 mg/dL | 1.50 mmol/L |
| 7.0 mg/dL | 1.75 mmol/L |
| 7.6 mg/dL | 1.90 mmol/L |
| 8.0 mg/dL | 2.00 mmol/L |
| 8.5 mg/dL | 2.12 mmol/L |
| 8.6 mg/dL | 2.15 mmol/L |
| 9.0 mg/dL | 2.25 mmol/L |
| 9.5 mg/dL | 2.37 mmol/L |
| 10.0 mg/dL | 2.50 mmol/L |
| 10.2 mg/dL | 2.54 mmol/L |
| 10.5 mg/dL | 2.62 mmol/L |
| 11.0 mg/dL | 2.74 mmol/L |
| 12.0 mg/dL | 2.99 mmol/L |
| 13.0 mg/dL | 3.24 mmol/L |
| 14.0 mg/dL | 3.49 mmol/L |
Normal Ionized Calcium and Total Calcium Levels
| Test (adults) | mmol/L | mg/dL |
|---|---|---|
| Ionized calcium (normal range) | 1.12 – 1.32 | 4.5 – 5.3 |
| Total calcium (normal range) | 2.15 – 2.55 | 8.6 – 10.2 |
| Low ionized calcium | below 1.12 | below 4.5 |
| High ionized calcium | above 1.32 | above 5.3 |
Reference ranges vary by lab and analyser. Use the range on your own report and discuss results with your doctor.
Ionized Calcium vs Total Calcium: Can You Convert One to the Other?
Not exactly. About half of the calcium in blood is ionized (free); the rest is bound to albumin and other molecules. A rough estimate is ionized calcium ≈ 45–50% of total calcium, but the true share changes with albumin, blood pH and kidney function, so a total calcium to ionized calcium calculator can only estimate. When accuracy matters, ionized calcium should be measured directly.
When albumin is low, doctors often use the corrected calcium formula instead:
- mg/dL: corrected calcium = total calcium + 0.8 × (4.0 − albumin in g/dL)
- mmol/L: corrected calcium = total calcium + 0.02 × (40 − albumin in g/L)
Example: total calcium 8.0 mg/dL with albumin 3.0 g/dL gives corrected calcium of 8.8 mg/dL (2.20 mmol/L).
Frequently Asked Questions
How do I convert ionized calcium mg/dL to mmol/L?
Divide by 4.008 (or multiply by 0.2495). For example, 5.0 mg/dL = 1.25 mmol/L.
What is 4.8 mg/dL ionized calcium in mmol/L?
4.8 mg/dL ÷ 4.008 = 1.20 mmol/L, within the normal range.
What is the formula to convert calcium mmol/L to mg/dL?
mg/dL = mmol/L × 4.008. For example, 2.34 mmol/L total calcium = 9.38 mg/dL, and 1.9 mmol/L = 7.62 mg/dL.
What is 8.5 mg/dL calcium in mmol/L?
8.5 mg/dL = 2.12 mmol/L, slightly below the usual total calcium range.
What is the normal ionized calcium range in mmol/L?
About 1.12–1.32 mmol/L (4.5–5.3 mg/dL).
How do I convert calcium mg/L to mmol/L?
Divide mg/L by 40.08. For example, 95 mg/L = 2.37 mmol/L. (mg/L = mg/dL × 10.)
How many mg is 1 mmol of calcium?
1 mmol of calcium = 40.08 mg. 2.25 mmol = 90.2 mg and 15 mmol = 601 mg.
Is calcium mmol/L the same as mEq/L?
No. Calcium has a +2 charge, so 1 mmol/L = 2 mEq/L.
Related: magnesium mmol/L to mg/dL and all electrolyte and mineral conversions. In Spanish and Portuguese, calcio iónico / cálcio ionizado mg/dL a mmol/L uses the same factor.