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Supplement Dose Calculator – Daily Intake vs Upper Limit

Enter one vitamin or mineral in this supplement dose calculator to see your daily amount as a percentage of the US and EU reference intake and upper limit.

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For information only, not medical advice. Reference values describe healthy population groups and do not tell you what dose you should take. Ask a doctor, pharmacist or dietitian before starting, stopping or combining supplements, especially if you are pregnant, take medication or have a health condition.

Reference values are for adults aged 19 and over. Children have different, lower limits. Sources: US Dietary Reference Intakes (NIH Office of Dietary Supplements) and EFSA Dietary Reference Values and Tolerable Upper Intake Levels (2024). Reviewed October 7, 2026.

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How to use the Supplement Dose Calculator

  1. 1 Choose the vitamin or mineral and enter the amount per serving from the label.
  2. 2 Select the unit – mg, µg, g or IU – and how many servings you take per day.
  3. 3 Enter your age and sex to compare the daily amount with the reference intake and the upper limit.

From label to daily amount

A label states the amount per serving, but what matters for safety is how much you take per day. The calculator multiplies the amount per serving by the number of servings and converts it to the unit used in the reference values. For vitamins A, D and E it also converts international units (IU): 1 µg of vitamin D is 40 IU, 1 µg RAE of vitamin A is 3.33 IU of retinol and 1 mg of natural vitamin E is about 1.49 IU.

Percentage of the reference intake

The reference intake (RDA, PRI or AI) is the amount that covers the needs of almost everyone in your age and sex group. A supplement does not have to provide 100%: you also get vitamins and minerals from food, and many supplements are designed to top up a normal diet rather than replace it.

Percentage of the upper limit

The upper limit (UL) is the highest daily intake that is unlikely to cause harm over the long term. The bar turns amber from 80% and red above 100% of an upper limit. Some examples of why the limits exist:

  • Vitamin B6 in high doses over months can cause nerve damage (peripheral neuropathy). The EU limit is 12 mg per day.
  • Vitamin A (retinol) in excess can harm the liver and, in pregnancy, the unborn child.
  • Zinc above the limit can lower copper levels.
  • Magnesium supplements above the limit commonly cause diarrhoea.

Not every nutrient has an upper limit; for vitamin B12, biotin and vitamin K no adverse effects were established at the levels studied, which does not mean unlimited amounts are useful.

One supplement or many?

This calculator looks at a single nutrient. If you take a multivitamin or several products, use the supplement stack calculator to add everything up and to spot nutrients that appear twice.

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Frequently asked questions

How many IU is 25 µg of vitamin D?

25 µg of vitamin D is 1,000 IU. Multiply micrograms by 40 to get IU.

Can I enter magnesium citrate?

This calculator expects the elemental amount, as on most labels. To convert a compound weight such as magnesium citrate, use the elemental mineral or magnesium calculator.

Why can I not choose IU for zinc?

International units are only defined for vitamins A, D and E. Minerals are always given in mg or µg.

Is 200% of the RDA dangerous?

Not in itself. What matters is whether you stay below the upper limit, which is often many times higher than the RDA.

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