Milligrams to Grams — Medication and Supplement Conversion Guide

Milligrams and grams show up constantly in healthcare, nutrition, and supplements — often in the same label. A bottle might say "500 mg per tablet" while a daily intake recommendation says "1 g per day." These are the same amount, but it is easy to lose track of the decimal places and accidentally miscalculate a dose.

The Weight Converter handles milligrams, grams, kilograms, and more. This article explains the relationship between mg and g, gives you a reference table for common medication and supplement amounts, and flags the places where getting the conversion wrong actually matters.

The Core Conversion

1 gram = 1,000 milligrams

1 milligram = 0.001 grams

grams = milligrams ÷ 1,000

milligrams = grams × 1,000

This is a clean power-of-10 relationship — the "milli-" prefix in the metric system always means one thousandth. So:

• 500 mg = 0.5 g
• 250 mg = 0.25 g
• 1,000 mg = 1 g
• 2,500 mg = 2.5 g

When a supplement label says "1,000 mg" and a dosage guide says "1 g daily," they are identical. The label is using milligrams because 1,000 looks more substantial than 1.0 (a well-known marketing practice in the supplement industry).

Milligrams to Grams Reference Table

Common Medication Doses in mg

Knowing typical medication doses helps you catch errors when reading prescriptions or packaging:

Paracetamol / Acetaminophen:

• Standard tablet: 500 mg
• Maximum single adult dose: 1,000 mg (1 g)
• Maximum daily dose (adult): 4,000 mg (4 g)
• Children's doses: 120–250 mg depending on weight and age

Ibuprofen:

• Standard OTC tablet: 200 mg or 400 mg
• Typical adult dose: 400 mg every 6–8 hours
• Maximum daily dose: 2,400 mg (non-prescription) or 3,200 mg (prescription)

Aspirin:

• Low-dose (antiplatelet, "baby aspirin"): 75–100 mg daily
• Standard tablet: 300–500 mg
• Maximum single dose: 1,000 mg

Antibiotics (common examples):

• Amoxicillin: 250 mg or 500 mg capsules, typically 500 mg 3× daily
• Penicillin V: 250–500 mg per dose
• Metronidazole: 400–500 mg per dose

This is general information, not a dosage guide. Always follow the prescriber's instructions and product labeling.

Common Supplement Doses in mg

Vitamin C:

• RDA: 75–90 mg/day
• Common supplements: 500–1,000 mg per tablet
• High-dose/therapeutic range: 1,000–2,000 mg/day

Magnesium:

• RDA: 310–420 mg/day depending on age and sex
• Common supplement dose: 200–400 mg per tablet
• Upper tolerable intake: 350 mg/day from supplements (food is fine above this)

Vitamin D:

• Measured in IU (International Units) or micrograms — not milligrams
• 1,000 IU = 25 micrograms (µg) — note this is micro, not milli
• Common supplements: 400 IU (10 µg) to 4,000 IU (100 µg)

Zinc:

• RDA: 8–11 mg/day
• Common supplements: 10–50 mg per tablet
• Upper tolerable intake: 40 mg/day

Iron:

• RDA: 8–18 mg/day (18 mg for premenopausal women)
• Therapeutic dose (iron deficiency): 100–200 mg elemental iron per day
• Common supplement: 14–65 mg elemental iron per tablet

Fish oil / Omega-3:

• Product labels typically list total fish oil (e.g., 1,000 mg), EPA content (e.g., 300 mg), and DHA content (e.g., 200 mg) separately
• Recommended intake of combined EPA+DHA: typically 250–500 mg/day for general health

Micrograms vs Milligrams — An Important Distinction

Milligrams (mg) and micrograms (µg or mcg) are easy to confuse, and the difference is a factor of 1,000.

• 1 mg = 1,000 µg
• 1 µg = 0.001 mg

Vitamins measured in micrograms include vitamin D, vitamin B12, folate (vitamin B9), and vitamin K. If a supplement label says "500 mcg" and you read it as milligrams, you would think you are getting 0.5 mg when you are actually getting 0.0005 mg — a factor of 1,000 off.

Medication errors involving mcg/mg confusion are well-documented in clinical settings. If you are ever unsure whether a dose is in mg or mcg, check the label again carefully. The abbreviation should be written out: either "mg" (milligrams) or "mcg" or "µg" (micrograms). The Greek letter µ looks similar to a lowercase "m" in some fonts, which is one source of confusion.

Daily Dietary Intake in mg

For context, here are common nutrients with typical daily intakes in milligrams. Most people consume these through food without counting the numbers, but they show up on nutrition labels.

Potassium at 3,500 mg/day is 3.5 g. Sodium at 2,300 mg/day is 2.3 g. These look more meaningful when converted to grams — it helps to have a sense of the physical amounts involved. A teaspoon of table salt contains roughly 2,300 mg of sodium.

Converting Between Milligrams and Other Units

For reference, here is where mg fits in the metric weight hierarchy:

• 1 kilogram (kg) = 1,000 grams = 1,000,000 milligrams
• 1 gram (g) = 1,000 milligrams
• 1 milligram (mg) = 0.001 grams = 0.000001 kilograms
• 1 microgram (µg) = 0.001 milligrams = 0.000001 grams

If you are doing nutrition label math, cooking, or checking supplement totals across multiple products, the Weight Converter handles the full range from micrograms to kilograms without requiring you to track the decimal places manually.