Milligram: Definition, Examples, and Practice Problems
reviewed by Jo-ann Caballes
Updated on January 13, 2026
As abstract as math is, it is also a practical science that your kid will often interact with in daily life. Measurements is one such math topic.
In this article, we will look into milligrams. The mg unit is part of the metric system, and chances are, you’ve already encountered it many times.
So, it’s time to review what mg is, mg measurement, conversion factors, and examples, as well as solve some exercises.
What is a milligram?
You can think of the milligram as one of the tiniest units in the math toolbox we use to measure how heavy things are. In simpler words, we use it to measure mass. The “mg” is the official milligram symbol.
As mentioned, milligram is an official unit of measurement in the metric system. We use milligrams when we need super-precise, super-small measurements. This is why you see it on so many important labels!
How much is a milligram?
The prefix “milli” is key to understanding milligram size. In the metric system, milli- always means one-thousandth (1/1000).
So, 1 milligram is simply one-thousandth of a gram. Or, to put it in other words, if you take 1 gram (already pretty light!), there are exactly 1000 milligrams in a gram.
What is mg unit?
As mentioned earlier, the unit of measurement for the milligram is the lowercase mg. It’s a universal unit, so no matter where you are, if you see an mg on a label, just know that you are dealing with a measurement of mass in milligrams.
Difference between grams and milligrams
The main difference, as you may have guessed, is the size! The gram is the base unit of mass. The milligram is the sub-unit that is 1000 times smaller.
As a relatively larger mass, we use grams for everyday objects like food ingredients. The milligram, on the other hand, is so small, it is reserved for incredibly small amounts, such as the active chemical in one tiny pill.
Are milligrams bigger than grams?
Absolutely not! Remember what a mg unit is? It’s 1/1000th of a gram. Because 1 gram equals 1000 milligrams, the milligram is significantly smaller. A simpler way to memorize this is to keep in mind that “milli” always means “small.”
Is mcg smaller than mg?
How many units is 1 mg, and which unit is smaller, are other common questions about mg. Let’s answer them briefly by introducing another unit, the mcg. McG stands for microgram, where “micro-” means one-millionth (1/1000000). This makes a microgram 1000 times smaller than a milligram. So, you need as many mcg units to get mg as you would need mg units to get a gram.
What is a milligram equal to?
To truly appreciate the milligram, we need to understand just how small it is in relation to other, more common units of measurement. To understand how many units are in a milligram, remember that 1 gram contains 1000 milligrams, so each milligram is 1/1000 of a gram. Now, to define milligrams based on its connection to the gram, we need to divide the gram by the number of mg units.
1 gram / 1000 milligrams = 0.001 grams.
1 milligram is 0.001 grams.
Measurement from and to
Movement from and to is a movement between two units. Let’s take the gram and milligram example here. During measurement, you either go from grams to milligrams or from milligrams to grams. You need to know which direction to take, as it will determine whether you multiply or divide by the conversion factor.
Conversion factor
A conversion factor is the number that links units (in our case, it’s grams and mg). Any guesses what that number is? If you said 1000, you are absolutely correct. It’s a critical number when you want to change mass units in the metric system.
- To convert grams to mg, multiply the number of grams by 1000, since 1gram = 1000mg.
- To convert mg to a gram, divide the number of milligrams by 1000, 1000 mg/1000 = 1gram.
Milligrams and other units of mass or weight
Naturally, grams, milligrams, and micrograms are not the only units of mass or weight in the metric system. In the table below, we list conversions between mg and some other units, to give you a better idea of what does a milligram look like.
|
Unit comparison (1 mg) to |
Conversion factor |
| Gram (g) | 1 mg = 1/1000 of a gram |
| Kilogram (kg) | 1 mg = 1/millionth of a kg |
| Microgram (mcg) | 1 mcg x 1000 = 1mg |
| Ounce (oz) | 1mg is about 0.000035 ounces |
| Pound (lb) | 1mg is about 0.0000022 pounds |
| Carat | 1 carat = 200mg |
This is far from an exhaustive list, but more common 5 things measured in milligrams you might have seen mgs in are food ingredients, vitamin dosage, medicine ingredients, skincare and haircare ingredients, and gemstones mass.
Things that weigh 1 mg
To give you an even better idea of just how tiny mg is, here are a few things that weigh 1 milligram.
- Trace amounts of medication
- Small quantities of vitamins
- Laboratory-scale measurements
Solved math tasks on milligram
1. A recipe calls for 0.85 grams of salt. How many milligrams is this?
Answer:
| 0.85 x 1000 = 850mg |
2. A small drop of liquid is 400 mg. What is the mass in grams?
Answer:
| 400mg/1000 = 0.4 grams |
3. There are 0.0001 kilograms of flour in a container. Express the mass in milligrams.
Answer:
| 0.0001 kg × 1,000,000 mg/kg = 100 mg |
4. How many kgs are 6500000 milligrams?
Answer:
| 6500000/1000000 (grams) = 6.5 kg |
Milligram: practice math problems
Conclusion
Now, you hopefully understand milligrams better than you did at the beginning of this article. Despite mg being a tiny unit, it’s essential for precise measurements in the real world. The main takeaway of the article is to remember the conversion factor, which is the number 1000, which will make mastering the conversion of mg to other units much easier. Good luck!
Frequently asked questions on milligrams
How big is a milligram?
A milligram is an extremely small unit and is defined as 1/1000th of a gram. The milligram is used to measure mass in practice, to weigh extremely small objects like a grain of salt.
How to calculate 1 milligram?
1 milligram is typically calculated based on its relations with the gram, and 1 g = 1000 mg. So, if you want to find how many mg a mass is, you need to multiply the mass by 1000. For example, 0.4 grams x 1000 = 400 mg.
How many mg is 1 ml?
You cannot convert mg to ml directly, as they measure different things. While mg shows mass, ml indicates volume (how much space something takes up), which often depends on the liquid’s density.
How many micrograms in a milligram?
Micrograms to a milligram is what milligrams are to a gram. There are 1000 micrograms in a milligram, the same way there are 1000 milligrams in a gram.
Milligram: Worksheets
Milligrams can be confusing at first, but with enough practice, your kid will get the hang of this measurement unit quite quickly. You can find many other challenging, yet fun, exercises in these free worksheets.
- 3rd grade measurement worksheets
- Metric conversion worksheets
- Metric system worksheets
- Measurement conversion worksheets
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