Vitamin unit converter: IU, mcg and mg
Founder of Clean Green Safe
Do the numbers on your vitamin label leave you scratching your head? You’re not alone. Choose your vitamin, enter the amount from your label, and you’ll see it in every unit, alongside the Australian daily target and upper limit.
Daily target for adults: 5 mcg (19–50), 10 mcg (51–70), 15 mcg (over 70)
Upper limit: 80 mcg (3,200 IU) a day
What does 1000 IU actually mean?
IU stands for International Unit. It’s an older way of measuring some vitamins, based on how active they are rather than how much they weigh. You’ll mostly see it on vitamin D, vitamin A and vitamin E.
For vitamin D, 1000 IU is the same as 25 mcg. It’s one of the most common doses on the shelf, so if you’ve seen it and wondered, you’re in very good company.
What is mcg in vitamins?
mcg means microgram, which is one millionth of a gram. Some vitamins are needed in such tiny amounts that milligrams (mg) would be too big a measure. One milligram is 1,000 micrograms, so 1000 mcg is the same as 1 mg.
Australian labels usually show vitamin D in micrograms. Products made for overseas markets often use IU, which is why the same dose can look so different from one bottle to the next.
Can you convert IU to mg?
Yes, but only for one vitamin at a time. Each vitamin has its own conversion, because IU measures activity, not weight. That’s why a single “IU to mg” number doesn’t exist, and why the calculator above asks you to choose the vitamin first.
- Vitamin D: 1 mcg = 40 IU, so 1000 IU = 25 mcg = 0.025 mg
- Vitamin A (retinol): 1 IU = 0.3 mcg
- Vitamin E (natural): 1 IU = 0.67 mg
- Vitamin E (synthetic): 1 IU = 0.45 mg
Quick reference for vitamin D
- 400 IU = 10 mcg
- 1000 IU = 25 mcg
- 2000 IU = 50 mcg
- 3200 IU = 80 mcg, the Australian upper limit for adults
- 5000 IU = 125 mcg, which is above the Australian upper limit
Some imported products follow higher overseas limits, so it’s worth checking the amount carefully, especially if you take more than one product with vitamin D. Our vitamin D guide explains the Australian daily targets in more detail.
How can I check my supplements are within safe limits?
- Note whether each label uses mcg, mg or IU, and convert if you need to.
- Multiply by the number of tablets or capsules you actually take each day.
- Add up every product that contains the same vitamin, including multivitamins.
If you’re unsure, or you take other medicines, please have a chat with your pharmacist or GP. We’re always happy to help you make sense of your labels.
Cassie is a registered pharmacist, a parent and the founder of Clean Green Safe. With a background in Australian supplement regulation across the TGA, FSANZ and NHMRC, she built Clean Green Safe to help people understand what’s really in their supplements, and how it all adds up across everything they take.
How Clean Green Safe can help
You don’t have to do these sums yourself. Scan any supplement and Clean Green Safe reads the label for you, whatever units it uses, and shows how each vitamin compares with your daily nutritional target and the Australian upper limit. Add everything you take to My Stack to see your daily totals in one place.
- STEP 1ScanScan the barcode or enter the AUST L number
- STEP 2CheckWe check it against the TGA register and Australian limits
- STEP 3SeeSee your grade and your daily totals across everything you take
Built by a registered pharmacist · Works in your phone’s browser