Salt to Base Conversion Table & Calculator

Reference table and two-way calculator for converting between salt forms and elemental/base equivalents. Covers calcium, magnesium, iron, fluoxetine, sildenafil, and more with conversion factors and clinical notes.

Disclaimer: This tool is provided for informational and educational purposes only. Results should always be independently verified by a qualified healthcare professional before use in clinical practice. Compound Direct accepts no liability for errors or clinical decisions made based on these calculations.

Section A: Reference Table

Browse and search salt-to-base conversion data

Filter by Category

Salt Form	Element/Base	MW (Salt)	MW (Base)	Factor	S:B Ratio
Azithromycin Dihydrate	Azithromycin	785.02	748.98	0.9541	1.05
Azithromycin Monohydrate	Azithromycin	767.00	748.98	0.9765	1.02
Calcium Carbonate	Calcium	100.09	40.08	0.4004	2.50
Calcium Chloride	Calcium	110.98	40.08	0.3611	2.77
Calcium Citrate	Calcium	498.43	40.08	0.0804	12.44
Calcium Gluconate	Calcium	430.37	40.08	0.0931	10.74
Calcium Lactate	Calcium	218.22	40.08	0.1837	5.44
Calcium Phosphate (Dibasic)	Calcium	172.09	40.08	0.2329	4.29
Cetirizine Dihydrochloride	Cetirizine	461.81	388.89	0.8421	1.19
Chromium Picolinate	Chromium	418.30	52.00	0.1243	8.04
Codeine Phosphate	Codeine	397.36	299.36	0.7534	1.33
Copper Gluconate	Copper	453.84	63.55	0.1400	7.14
Copper Sulfate	Copper	159.61	63.55	0.3982	2.51
Ferrous Fumarate	Iron	169.90	55.85	0.3287	3.04
Ferrous Gluconate	Iron	446.14	55.85	0.1252	7.99
Ferrous Sulfate	Iron	151.91	55.85	0.3677	2.72
Ferrous Sulfate (Dried)	Iron	151.91	55.85	0.3677	2.72
Fluoxetine Hydrochloride	Fluoxetine	345.79	309.33	0.8946	1.12
Magnesium Chloride	Magnesium	95.21	24.31	0.2553	3.92
Magnesium Citrate	Magnesium	214.41	24.31	0.1134	8.82
Magnesium Glycinate	Magnesium	172.42	24.31	0.1410	7.09
Magnesium Orotate	Magnesium	334.48	24.31	0.0727	13.76
Magnesium Oxide	Magnesium	40.30	24.31	0.6032	1.66
Magnesium Sulfate	Magnesium	120.37	24.31	0.2020	4.95
Magnesium Taurate	Magnesium	272.57	24.31	0.0892	11.21
Manganese Gluconate	Manganese	445.23	54.94	0.1234	8.10
Manganese Sulfate	Manganese	151.00	54.94	0.3638	2.75
Metformin Hydrochloride	Metformin	165.63	129.16	0.7798	1.28
Morphine Sulfate	Morphine	668.76	285.34	0.4267	2.34
Naltrexone Hydrochloride	Naltrexone	377.86	341.40	0.9035	1.11
Potassium Bicarbonate	Potassium	100.12	39.10	0.3905	2.56
Potassium Chloride	Potassium	74.55	39.10	0.5245	1.91
Potassium Citrate	Potassium	306.39	39.10	0.1276	7.84
Potassium Gluconate	Potassium	234.25	39.10	0.1669	5.99
Prednisolone Sodium Phosphate	Prednisolone	484.39	360.44	0.7441	1.34
Selenomethionine	Selenium	196.11	78.97	0.4027	2.48
Sertraline Hydrochloride	Sertraline	342.69	306.23	0.8936	1.12
Sildenafil Citrate	Sildenafil	666.70	474.58	0.7118	1.40
Sodium Selenite	Selenium	172.94	78.97	0.4566	2.19
Trazodone Hydrochloride	Trazodone	408.32	371.86	0.9107	1.10
Venlafaxine Hydrochloride	Venlafaxine	313.86	277.40	0.8838	1.13
Zinc Gluconate	Zinc	455.68	65.38	0.1435	6.97
Zinc Oxide	Zinc	81.38	65.38	0.8034	1.24
Zinc Picolinate	Zinc	309.60	65.38	0.2112	4.74
Zinc Sulfate	Zinc	287.56	65.38	0.2274	4.40

45 of 45 conversions shown

Section B: Two-Way Calculator

Convert between salt and elemental/base amounts

Select Salt Form

Element: Azithromycin

Conversion Factor: 0.9541

Azithromycin Dihydrate (mg)

Azithromycin (mg)

How to Use This Tool

Reference Table

Use the category filter tabs to view specific element types (Calcium, Magnesium, Iron, Other)
Search by salt name, element, or category using the search box
Review the molecular weights, conversion factor, and notes for each salt form
Check the notes column for clinical guidance on each salt form

Calculator

Select a salt form from the dropdown
Enter either the salt amount (mg) or base/elemental amount (mg)
The calculator automatically converts to the other unit
Use results for compounding prescriptions, supplement labeling, or dosing comparisons

Formula & Methodology

Molecular Weight Ratio

Salt-to-base conversions are based on the molar ratio of molecular weights. When a drug is formulated as a salt (e.g., calcium carbonate), only a fraction of the weight is the active element or base.

Conversion Factor Formula:

Factor = MW(Base) / MW(Salt)

Salt-to-Base Ratio:

S:B Ratio = 1 / Factor = MW(Salt) / MW(Base)

Example: Calcium Carbonate

Factor = 40.08 / 100.09 = 0.4

S:B Ratio = 1 / 0.4 = 2.50

Therefore: 500 mg CaCO₃ × 0.4 = 200 mg Ca²⁺

Why Salt Forms Matter

Different salt forms of the same element have different bioavailability, gastrointestinal tolerance, and therapeutic efficacy. Some key considerations:

Bioavailability: Some salts are absorbed better (e.g., citrate vs. oxide)
Molecular Weight: Lighter salts deliver more active element per gram (e.g., fumarate vs. gluconate iron)
GI Tolerability: Some salts cause fewer GI side effects (e.g., glycinate magnesium vs. oxide)
Compliance: Different strengths and dosing frequencies may be available for each salt form

Clinical Application

Understanding salt-to-base conversions is essential for compounding pharmacy, evaluating supplements, comparing drug formulations, and ensuring accurate dosing when switching between salt forms of the same active element.

Frequently Asked Questions

Why do medications have different salt forms?

Salt forms are used to improve stability, increase bioavailability, or reduce side effects. For example, calcium carbonate is inexpensive but requires stomach acid for absorption, while calcium citrate does not. Different salt forms may have different dosing frequencies and tolerance profiles.

How are conversion factors calculated?

Conversion factors are calculated using the ratio of molecular weights: Factor = Molecular Weight of Element / Molecular Weight of Salt. For example, calcium carbonate (CaCO₃, MW=100.09) has a conversion factor of 40.08/100.09 = 0.4, meaning 500 mg CaCO₃ provides 200 mg of elemental calcium.

What is the difference between calcium citrate and calcium carbonate?

Calcium carbonate requires stomach acid for absorption and is best taken with food, making it inexpensive but less convenient. Calcium citrate is absorbed better in low-acid conditions and can be taken without food. However, calcium carbonate contains more elemental calcium per dose (40% vs 21%), so fewer pills may be required. Choice depends on patient tolerance, food intake, and medication interactions.

Why do iron supplements vary so much in elemental iron content?

Different iron salts have different molecular weights, so they deliver varying amounts of elemental iron. Ferrous sulfate provides 20-33% elemental iron by weight, while ferrous gluconate provides only 12%. This is why comparing iron supplements requires understanding the salt form and looking at elemental iron, not just the dose listed on the label.

Is it safe to switch between different salt forms of the same element?

Yes, switching salt forms is clinically appropriate as long as the elemental content is equivalent. However, bioavailability and GI tolerance may differ. Always verify elemental content and consult the prescriber if the patient experiences changes in symptoms or tolerability after switching salt forms.

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