Vitamin D IU to mcg Converter
A vitamin D capsule marked 1,000 IU holds 25 mcg, because 1 mcg of vitamin D equals 40 IU.
Quick answer: Divide the IU by 40. For example, 1,000 IU is 25 mcg, 400 IU is 10 mcg and 600 IU is 15 mcg.
The vitamin D IU to mcg formula
Micrograms equal the IU divided by 40.
The number 40 only works for vitamin D. Other vitamins use other factors.
Take 1,000 IU. 1,000 ÷ 40 gives 25 mcg.
Take 400 IU. 400 ÷ 40 gives 10 mcg.
Why vitamin D uses two units
The international unit, or IU, measures how strong a substance is in the body. It is not a unit of weight (chemeurope: International unit).
For vitamin D, one IU was fixed at 0.025 mcg, so 40 IU make 1 mcg. Many labels now show both numbers side by side.
How to convert vitamin D IU to mcg step by step
- Find the IU on the label.
- Divide it by 40.
- Write the answer in mcg.
- To get mg, divide the mcg by 1,000.
Example 1: 1,000 IU
- Start with 1,000 IU.
- 1,000 ÷ 40 = 25.
- The amount is 25 mcg.
1,000 IU = 25 mcg
Example 2: 400 IU
- Start with 400 IU.
- 400 ÷ 40 = 10.
- The amount is 10 mcg.
400 IU = 10 mcg
Example 3: 600 IU
- Start with 600 IU.
- 600 ÷ 40 = 15.
- The amount is 15 mcg.
600 IU = 15 mcg
Example 4: 2,000 IU
- Start with 2,000 IU.
- 2,000 ÷ 40 = 50.
- The amount is 50 mcg.
2,000 IU = 50 mcg
Example 5: 5,000 IU
- Start with 5,000 IU.
- 5,000 ÷ 40 = 125.
- The amount is 125 mcg.
5,000 IU = 125 mcg
Example 6: 800 IU
- Start with 800 IU.
- 800 ÷ 40 = 20.
- The amount is 20 mcg.
800 IU = 20 mcg
Check that the label says vitamin D and not another vitamin, since each has its own factor.
vitamin D IU to mcg conversion table
| Vitamin D (IU) | Vitamin D (mcg) | Vitamin D (mg) |
|---|---|---|
| 100 IU | 2.5 mcg | 0.0025 mg |
| 200 IU | 5 mcg | 0.005 mg |
| 400 IU | 10 mcg | 0.01 mg |
| 600 IU | 15 mcg | 0.015 mg |
| 800 IU | 20 mcg | 0.02 mg |
| 1,000 IU | 25 mcg | 0.025 mg |
| 2,000 IU | 50 mcg | 0.05 mg |
| 4,000 IU | 100 mcg | 0.1 mg |
| 5,000 IU | 125 mcg | 0.125 mg |
| 10,000 IU | 250 mcg | 0.25 mg |
The highlighted row is the default of the calculator. The last column gives Milligrams (mg).
A quick mental shortcut for vitamin D IU to mcg
Divide by 40 in two easy steps. Divide by 4, then by 10.
So 2,000 IU is 500 after dividing by 4, and 50 mcg after dividing by 10.
Reading a supplement label
Many bottles list both units, for example 25 mcg (1,000 IU). The two numbers describe the same amount.
If a label shows only IU, use this page to see the weight. If it shows only mcg, use the mcg to IU page.
Quick conversion answers
| Conversion | Result |
|---|---|
| 400 IU | 10 mcg |
| 1,000 IU | 25 mcg |
| 2,000 IU | 50 mcg |
| 5,000 IU | 125 mcg |
Where this conversion is used
Shoppers compare supplements that list IU with ones that list mcg.
People match a doctor note in IU with a bottle in mcg.
Common mistakes to avoid
- Using 40 for another vitamin. Vitamin A and E use different factors.
- Multiplying by 40. Going from IU to mcg means dividing.
- Mixing mcg and mg. 1 mg is 1,000 mcg.
- Reading mcg as mg. A 25 mcg dose is 0.025 mg, not 25 mg.
Related converters
More amounts at a glance
300 IU is 7.5 mcg. 500 IU is 12.5 mcg. 700 IU is 17.5 mcg.
1,500 IU is 37.5 mcg. 3,000 IU is 75 mcg. 6,000 IU is 150 mcg.
7,000 IU is 175 mcg. 8,000 IU is 200 mcg. 50,000 IU is 1,250 mcg.
Why labels changed
Many countries now list vitamin D in mcg. The IU figure is still printed beside it so that older labels and newer ones can be compared.
The amount of vitamin D does not change when you switch units. Only the number you read changes.
Common bottle sizes
A 400 IU tablet holds 10 mcg of vitamin D. A 1,000 IU softgel holds 25 mcg, and a 2,000 IU softgel holds 50 mcg.
A 5,000 IU softgel holds 125 mcg. A 50,000 IU capsule holds 1,250 mcg, which is 1.25 mg.
Daily totals over a week
If a label gives 1,000 IU a day, a week adds up to 7,000 IU, which is 175 mcg. At 2,000 IU a day the week adds up to 14,000 IU, or 350 mcg.
The same weekly total is easy to see in either unit once you divide by 40.
Checking the answer
To check a result, multiply the mcg by 40. For 25 mcg that gives 1,000 IU, which is where you started.
If the check does not match, look for a slipped decimal point.
Rounding on labels
Some IU amounts do not give a whole number of mcg. 500 IU is exactly 12.5 mcg, and 300 IU is 7.5 mcg.
Labels often round these to the nearest whole mcg, so the printed figure may differ slightly from the exact sum.
Half and double
Half of 1,000 IU is 500 IU, which is 12.5 mcg. Double 1,000 IU is 2,000 IU, which is 50 mcg.
The conversion is a straight line, so any change in IU gives the same change in mcg.
Frequently asked questions
How many mcg is 1,000 IU of vitamin D?
25 mcg.
How many mcg is 400 IU of vitamin D?
10 mcg.
How many mg is 1,000 IU of vitamin D?
0.025 mg.
Why divide by 40?
Because 1 mcg of vitamin D equals 40 IU.
Is the same factor used for vitamin A?
No. Vitamin A uses about 0.3 mcg per IU for retinol.
Is IU a unit of weight?
No. It measures biological strength, so each substance has its own factor.
Sources
- chemeurope: International unit (chemeurope.com)
- People’s Pharmacy: How Many Units in a Milligram (library.peoplespharmacy.com)
Medical note: This page is a unit converter, not medical advice. It does not tell you how much to take or to inject. Check your product label, and ask your doctor or pharmacist before you use any number from here.
Supplements differ in strength. Ask your doctor before you change how much you take.
