How much drops is 100 mL?

100 mL is a common volume measurement used in recipes, medical dosages, and scientific experiments. But how does this volume translate into the number of drops, which is a more precise way of measuring small amounts of liquid? In this comprehensive guide, we will explore the relationship between milliliters (mL) and drops and provide calculations to determine the number of drops in 100 mL of liquid.

What is a Milliliter?

A milliliter (mL) is a unit of volume equal to 1 cubic centimeter (cm3). One milliliter takes up the same space as a 1 cm x 1 cm x 1 cm cube. There are 1000 milliliters in one liter. The milliliter is commonly used for measuring volumes of liquids in recipes, medication dosages, chemical solutions, and scientific experiments.

Some key facts about the milliliter:

• 1 mL = 0.001 L = 1 cm3
• 1 mL is equal to about 0.034 U.S. fluid ounces
• 1 mL of water has a mass of 1 gram
• Milliliters are part of the metric system and are used worldwide, except in the United States where fluid ounces are more common

The milliliter allows for precise measurement of small volumes of liquids, down to fractions of a milliliter. It is one of the most common units used by scientists, doctors, and cooks for measuring liquid ingredients and chemical reagents.

What is a Drop?

A drop is an informal unit of very small liquid volume. Drops are not standardized, so the volume of one drop can vary greatly depending on the type of liquid, dropper or pipette used, and technique. However, a typical drop from a dropper is estimated to be around 0.05 mL – 0.1 mL.

• There is no universal definition of a drop’s volume
• Volume can range from 0.05-0.1 mL, or 5-10 drops per mL
• Viscous liquids like oils form larger drops
• Drop size depends on orifice diameter, surface tension, speed, etc.
• In medicine, a “drop” from an eyedropper is often 0.05 mL

While not a formal SI unit, a drop is sometimes a more convenient way to measure tiny amounts of a liquid, especially in medicine and chemistry. However drops can vary significantly in size, so they are not ideal for precision.

Converting Between Milliliters and Drops

Since the drop is an informal unit, there is no universal conversion factor between mL and drops. However, based on the typical estimate of 5-10 drops per mL, we can make the following general conversions:

• 1 mL = 5-10 drops
• 100 mL = 500-1000 drops

To convert between milliliters and drops, you can use the following general rules of thumb:

Milliliters to Drops Conversion

• Use 10 drops per 1 mL as a high estimate
• Use 5 drops per 1 mL as a low estimate

So for 100 mL:

• High estimate: 100 mL x 10 drops/mL = 1000 drops
• Low estimate: 100 mL x 5 drops/mL = 500 drops

Drops to Milliliters Conversion

• Use 1 mL per 10 drops for a high estimate
• Use 1 mL per 5 drops for a low estimate

So for 500 drops:

• High estimate: 500 drops / 10 drops/mL = 50 mL
• Low estimate: 500 drops / 5 drops/mL = 100 mL

Keep in mind that these conversions provide only rough estimates. For greater precision, you must measure the actual volume of drops from your specific dropper setup and liquid.

How to precisely calculate drops per mL

To accurately convert between millileters and drops, you should experimentally determine the number of drops per milliliter for your specific situation. Here is a simple procedure:

1. Select a clean pipette or dropper for dispensing your liquid.
2. Set up a small container or vial and pipette/dropper over it to collect drops.
3. Use the pipette/dropper to dispense drops of the liquid into the container, counting each drop.
4. After dispensing around 50-100 drops, use a small metric measuring cup or syringe to measure the volume collected.
5. Divide the number of drops dispensed by the volume collected in mL. This gives you drops per mL.
6. Repeat steps 2-5 several times to get an average drops per mL conversion factor.

Be sure to get an average from multiple tests, as results can vary. This controlled experiment will give you a precise drops-to-milliliters conversion factor tailored to your specific setup and liquid.

Variables that affect drop size

Many factors can affect the volume of an individual drop. These variables should be controlled as much as possible when determining drops per milliliter for a given setup:

Liquid properties

• Viscosity – Viscous liquids like oils form larger drops than watery liquids.
• Surface tension – Liquids with higher surface tension produce larger drops.
• Temperature – Heated liquids tend to have lower viscosity and surface tension, resulting in smaller drops.
• Evaporation – Fast evaporating liquids shrink droplets as they form.

Equipment factors

• Orifice diameter – Larger bore pipette tips or droppers produce larger drops.
• Drop height – Drops falling from greater height tend to elongate and fragment.
• Delivery speed – Quickly dispensed drops are usually smaller.
• Angle – Vertical drops are more uniform than angled drops.

Technique

• Touching surface – Contacting a surface as the drop forms can remove trailing liquid and decrease volume.
• Accumulated drips – Letting drips accumulate before dropping also gives larger drops.

Automated precision liquid handling systems produce the most uniform drop sizes by controlling these variables. But understanding these factors allows you to get relatively consistent drop volumes.

Typical drop sizes of common liquids

As a point of reference, here are some typical drop sizes for common laboratory and household liquids:

Liquid Viscosity at 20°C (cP) Surface Tension at 20°C (mN/m) Typical Drops per mL
Water 1.0 72.8 55-65
Ethanol 1.2 22.7 110-130
Olive oil 84 32.0 25-30
Honey 10,000 70.0 35-45
Whole blood 4.8 63.5 55-65
Mercury 1.526 486 28-32

As shown above, less viscous liquids with lower surface tension like ethanol have the most drops per milliliter. Viscous liquids like oils and honey have larger drops. But these serve only as rough estimates, so measuring your specific drops per milliliter will give the most accurate results.

Common use cases for milliliter to drop conversions

Recipes and cooking

Some recipes call for very small liquid volumes like extracts or flavorings in drops rather than millileters. Converting the recipe volumes to drops can be helpful. Just be aware that different viscosities and dropper tips will affect your results.

DIY e-liquid mixing

Many people prepare their own vape e-liquids at home. Vape recipes specify volumes in millileters which must be converted based on the user’s droppers and ingredients. Averages of ~15 drops per mL are common.

Essential oil usage

Essential oils are often packaged with dropper caps, and aromatherapy recipes specify the oil volumes in drops. Knowing the density allows converting from volume measurements to drops for precise mixing.

Tinctures and concentrates

Solutions like herbal tinctures, hemp extracts, and chemical stock solutions are often prepared using volumes. However, the final products are packaged with droppers for convenient dosing. Conversions facilitate precise concentration preparation.

Titrating solutions

In chemistry lab work, solutions of reagents are titrated by carefully dripping small volumes into a reaction mixture and observing the change. Knowing your drop factor helps accurately titrate and dispense volumes.

Medicine and pharmaceuticals

Many liquid drugs, supplements, and nutraceuticals are packaged with a dropper for dosing by patients at home. The concentrations are designed to deliver therapeutic amounts in certain drop volumes.

Tips for dispensing accurate drop volumes

While calculating drops per milliliter is important, proper technique is also essential for precision. Here are some tips for accurately dispensing drops:

• Work slowly and carefully to control drop rate
• Keep the dropper vertical throughout dispensing
• Dispense drops from a consistent height above the container
• Let drops fall straight down without touching anything
• Allow the entire drop to form before releasing
• Remove any residual liquid on the dropper tip between drops
• Visually confirm each full drop enters the container
• Avoid build up dripping down the outside of the dropper

Automated dispensers such as burettes, pipettes, and peristaltic pumps offer the best drop accuracy and precision. But proper manual technique allows surprisingly good results.

Conclusion

In summary, there is no set conversion between milliliters (mL) and drops because drops are not a formal unit and can vary in size. However, typical estimates are:

• 1 mL = 5-10 drops
• 100 mL = 500-1000 drops

For accuracy, the ideal method is to experimentally determine the specific number of drops per milliliter based on your equipment, technique, and liquids. Controlling drop size variability and using good dispensing technique allows milliliter volumes to be precisely dispensed by drops.