Milligrams and milliliters are two units of measurement commonly used in science, medicine, and pharmacology. A milligram (mg) is a unit of mass, while a milliliter (mL) is a unit of volume. To understand how many milligrams are in a milliliter, it’s important to first understand these units and how they relate to each other.

In short, there are 1000 mg in 1 mL of water. However, this conversion depends on the density of the substance in question. The density of a substance relates its mass to its volume. For water at room temperature, the density is approximately 1 g/mL. Because 1 g = 1000 mg, there are 1000 mg in 1 mL of water. But for other liquids or solutions, the density may differ, so the mg per mL will also differ. Keep reading for more details on converting between milligrams and milliliters.

## What is a Milligram?

A milligram (mg) is a unit of mass in the metric system. It is equal to one thousandth of a gram. The milligram is commonly used in science and medicine to express very small masses of substances like pharmaceutical drugs, vitamins, or nutrients.

For example, many tablets and capsules contain active ingredients in milligram amounts like 500 mg or 250 mg. The small size of the milligram allows for precise measurement of these tiny amounts of substances. Some equivalents to the milligram are:

– 1 mg = 0.001 g

– 1000 mg = 1 g

– 1 mg = 1000 μg (micrograms)

The milligram is often used with the SI prefixes that scale the units up or down:

– Kilogram (kg) = 1000 g

– Gram (g) = 1000 mg

– Milligram (mg) = 1000 μg

– Microgram (μg) = 0.001 mg

So you can express larger or smaller masses by scaling the milligram up to grams and kilograms or down to micrograms. But the milligram itself represents an extremely tiny amount of mass suitable for measuring medicines, vitamins, and other substances used in minute quantities.

## What is a Milliliter?

A milliliter (mL) is a unit of volume in the metric system equal to one thousandth of a liter. It is used to measure small volumes of liquid. Some common equivalents are:

– 1 mL = 0.001 L

– 1000 mL = 1 L

– 1 mL = 1 cm3 (cubic centimeter) for water at 4°C

Like the milligram, the milliliter is commonly combined with SI prefixes:

– Kiloliter (kL) = 1000 L

– Liter (L) = 1000 mL

– Milliliter (mL) = 0.001 L

– Microliter (μL) = 0.001 mL

So you can measure larger or smaller volumes by scaling up to liters and kiloliters or down to microliters. On its own, the milliliter allows precise measurement of small amounts of liquids, especially in medicine and chemistry. For example, doses of liquid medications are often measured in milliliters.

The milliliter is also a unit of capacity in cooking and nutrition. Ingredients like vanilla extract, lemon juice, and milk are often measured in teaspoons (5 mL), tablespoons (15 mL) or cups (250 mL).

## Converting Between Milligrams and Milliliters

So how can you convert between milligrams and milliliters? The conversion depends on the density of the substance in question.

Density relates mass to volume. It is calculated by dividing the mass of a substance by its volume. This gives a measure of how much mass fits into a certain volume. Substances with a higher density have more mass packed into the same volume.

The density of water at room temperature is approximately 1 gram per milliliter, or 1 g/mL. Since 1 gram = 1000 milligrams, there are 1000 milligrams in 1 milliliter of water.

Therefore, for water at room temperature:

1000 mg = 1 g

1 g = 1 mL

So, 1000 mg = 1 mL

This makes converting easy. To go from milliliters to milligrams, you multiply by 1000. To go from milligrams to milliliters, you divide by 1000.

For example:

– 500 mg = 0.5 mL

– 250 mL = 250,000 mg

### Density of Other Substances

While water has a density of approximately 1 g/mL at room temperature, other substances may have different densities. Here are some examples:

– Ethanol (alcohol): 0.789 g/mL

– Glycerol (glycerin): 1.261 g/mL

– Mercury: 13.534 g/mL

– Honey: 1.42 g/mL

To convert between milligrams and milliliters for substances other than water, you first need to know their density in g/mL. Then you can use their density in the conversion instead of 1 g/mL for water.

For ethanol with a density of 0.789 g/mL:

0.789 g = 1 mL

0.789 g x 1000 mg/g = 789 mg

So for ethanol, 789 mg = 1 mL

For mercury with density 13.534 g/mL:

13.534 g = 1 mL

13.534 g x 1000 mg/g = 13,534 mg

So for mercury, 13,534 mg = 1 mL

So for substances other than water, you’ll need to multiply or divide by their specific density in g/mL instead of 1 g/mL when converting between milligrams and milliliters.

## Concentrations Expressed in Milligrams per Milliliter

In chemistry, medicine, and pharmacology, you’ll often see concentrations of solutions expressed in milligrams per milliliter or mg/mL. This gives a measure of how much of a dissolved substance is present in a solution.

Some examples of concentrations in mg/mL:

– 20 mg/mL vitamin C solution

– 50 mg/mL morphine solution

– 250 mg/5mL amoxicillin suspension

To make a solution with a specific concentration in mg/mL, you calculate the weight of solute needed based on the final desired volume of solution.

For example, to make 100 mL of a 50 mg/mL morphine solution, you would need 5000 mg of morphine (100 mL x 50 mg/mL = 5000 mg).

Concentrations in mg/mL allow precise dosing when administering drug solutions. Using the morphine example, you could administer a 2 mg dose by giving 0.04 mL of the 50 mg/mL solution (0.04 mL x 50 mg/mL = 2 mg).

## Milligrams per Milliliter to Mass Percent Concentration

Another common way to express the concentration of solutions is using mass percent or mass/volume percent. This is the mass of a solute divided by the total mass of the solution, multiplied by 100%.

You can convert between mg/mL and mass percent concentrations using the density of the solution.

For example, a 10 mg/mL salt solution has density 1.05 g/mL.

10 mg/mL = 10 mg salt per 1 mL solution

1.05 g/mL is the density of the solution

To convert to mass %:

10 mg salt / 1.05 g solution x 100% = 0.95%

So 10 mg/mL = 0.95% mass/volume

And to go the other direction from mass percent to mg/mL, you would divide the mass percent by 100% first:

0.95% / 100% = 0.0095 g salt per 1 g solution

Then use the density to convert back to milligrams per milliliter:

0.0095 g/mL x 1000 mg/g = 9.5 mg/mL

So 0.95% = 9.5 mg/mL

Converting between these concentration units comes in handy in chemistry and medicine when working with different solute solutions.

## Milliequivalents Compared to Milligrams and Milliliters

Another unit you may encounter is the milliequivalent or mEq. This is used to measure the amount or concentration of ions in solution.

One milliequivalent is the number of milligrams of an ion that corresponds to its equivalent weight. The equivalent weight relates to the electrical charge of the ion.

For example, for calcium (Ca2+), the equivalent weight is one half its atomic weight since it has a 2+ charge. With atomic weight 40, the equivalent weight of Ca2+ is 20.

Therefore, 1 mEq of Ca2+ is 20 mg.

For chloride (Cl-), the equivalent weight equals its atomic weight since it has a 1- charge. With atomic weight 35.5, 35.5 mg Cl- = 1 mEq.

So for ions, the milliequivalent allows you to account for their charge when measuring amounts. It combines aspects of mass in milligrams and chemical equivalence.

To summarize:

– 1 mEq Ca2+ = 20 mg

– 1 mEq Cl- = 35.5 mg

You can also get concentrations in mEq/mL for solutions, like a saline IV bag labeled “150 mEq/L NaCl”. This tells you the concentration of ionic sodium and chloride in the solution.

Milliequivalents are convenient shorthand for measuring ionic concentrations compared to the mass in milligrams. They also connect to the relative chemical reactivity of the ions. So you may see milliequivalents used for salts, acids and bases, and other ionic solutions.

## Practical Examples of Milligram and Milliliter Conversions

Being able to convert between milligrams, milliliters, and concentrations in mg/mL is very useful for medicine, pharmacology, chemistry, cooking and more. Here are some practical examples:

### Pharmacology and Drug Dosing

– A prescription calls for 1.5 g of amoxicillin 3 times a day. The amoxicillin suspension comes as 400 mg/5 mL. How many mL should be taken each dose?

First convert 1.5 g to mg: 1.5 g x 1000 mg/g = 1500 mg

The suspension has 400 mg in 5 mL.

So to get 1500 mg you would need:

1500 mg / 400 mg/5 mL = 3.75 mL

Round up to the nearest mL and take 4 mL per dose.

– A dexamethasone solution has a concentration of 4 mg/mL. How many mL contains 16 mg of dexamethasone?

Use the ratio: 4 mg in 1 mL

16 mg is the unknown number of mL

Set up a proportion:

4 mg/1 mL = 16 mg/x mL

Solve to find x = 4 mL

So 16 mg is contained in 4 mL of 4 mg/mL dexamethasone solution.

### Determining IV Flow Rates

– An IV bag has 250 mL of saline with 150 mEq of sodium chloride. It should infuse over 2 hours. What is the flow rate in mL/hr?

250 mL over 2 hours

Divide 250 mL by 2 hours to get the flow rate:

250 mL / 2 hr = 125 mL/hr

So set the IV pump to infuse at 125 mL/hr

– An IV contains 600 mg of penicillin in 250 mL normal saline. Infuse over 6 hours. What is the flow rate in mg/hr?

First calculate the concentration:

600 mg in 250 mL = 2.4 mg/mL

Flow rate is 250 mL over 6 hours

250 mL / 6 hr = 41.7 mL/hr

To convert the flow rate to mg/hr:

2.4 mg/mL x 41.7 mL/hr = 100 mg/hr

Set the pump to deliver 100 mg/hr

### Cooking and Mixing Drinks with mL and mg

– A recipe calls for 2 teaspoons (10 mL) of vanilla. If vanilla extract is 35 mg/mL, how many mg of vanilla flavoring is needed?

10 mL x 35 mg/mL = 350 mg of vanilla extract

– A drink recipe requires 150 mg of CBD oil in 30 mL of smoothie. What concentration of CBD oil in mg/mL should be used?

Set up a ratio:

x mg CBD/1 mL smoothie = 150 mg CBD/30 mL smoothie

x = 150 mg CBD / 30 mL smoothie

x = 5 mg/mL

So a 5 mg/mL CBD oil would provide 150 mg CBD in 30 mL of smoothie.

## Key Points

– A milligram (mg) is a unit of mass while a milliliter (mL) is a unit of volume.

– There are 1000 mg in 1 mL of water since it has a density of 1 g/mL (and 1 g = 1000 mg)

– For other liquids or solutions, density may differ from 1 g/mL, so the mg per mL will also differ.

– You can convert between mg, mL, and concentrations in mg/mL by using the density in g/mL.

– Milliequivalents (mEq) represent the equivalent mass of ions accounting for their charge.

– Converting between units comes in handy for medicine, pharmacology, chemistry, and cooking applications.

## Conclusion

Milligrams and milliliters allow precise measurement of very small masses and volumes that are commonly used in science and medicine. While milligrams measure mass and milliliters measure volume, you can convert between the two units using density, which relates mass to volume.

For water at room temperature with a density of 1 g/mL, there are 1000 milligrams in 1 milliliter. For other substances, the density must be taken into account during conversion based on how many grams are present in 1 mL. Additionally, concentrations can be expressed in milligrams per milliliter to represent the mass of solute dissolved in a liquid. Converting between mass, volume, and concentration units aids in medicine, pharmacology, chemistry, and cooking applications where precise measurement of small quantities is needed.