Drops to mL Conversion Calculator
Convert drops (gtt) to milliliters instantly. Adjustable drop factor for medical, laboratory, cosmetic, and DIY applications.
What the drops to mL converter does
The drops to millilitres converter turns a count of drops into a volume. Enter the number of drops and the drop factor, which is how many drops make one millilitre for the dropper or tubing you are using, then press Calculate. The result is the volume in millilitres. The default drop factor of 20 matches the most common IV administration set and the pharmacy convention for aqueous drops.
The formula
mL = drops ÷ drop factor (drops per mL)
Twenty drops at a factor of 20 is exactly 1 mL. Sixty drops at a factor of 60 is also 1 mL, which is why the drop factor has to be entered rather than assumed.
Why the drop factor varies
A drop is not a fixed unit. Its size depends on the orifice of the dropper, the surface tension and viscosity of the liquid, and how fast it is dispensed. Common values:
| Source | Drops per mL | Notes |
|---|---|---|
| Standard (macrodrip) IV set | 10, 15 or 20 | Printed on the packaging; 20 is common outside North America |
| Microdrip IV set | 60 | Paediatric and precise infusions |
| Pharmacy convention, water-based | 20 | Basis of the old “gtt” prescriptions |
| Glass eyedropper, water | About 20 | Larger drops from a wide tip |
| Ophthalmic squeeze bottle | 25 to 35 | Manufacturer specific |
| Essential oil dropper (orifice reducer) | 25 to 40 | Thicker oils give smaller drops |
| Ethanol or thin tinctures | About 40 to 60 | Low surface tension makes very small drops |
Worked examples
Infusion counting. A nurse counts 30 drops in a minute from a 20 drop/mL set. That is 30 ÷ 20 = 1.5 mL per minute, or 90 mL per hour.
Eye drops per bottle. A 5 mL bottle at 30 drops/mL holds about 150 drops; at one drop in each eye twice a day it lasts 37 days.
Aromatherapy blend. 12 drops of essential oil at 30 drops/mL is 0.4 mL. In 20 mL of carrier oil that is a 2% dilution.
Tincture dose. 40 drops at 50 drops/mL is 0.8 mL. If the label says 1 mL per dose, you are 20% under.
Going the other way
Drops = mL × drop factor. To draw 2.5 mL with a 20 drop/mL dropper you need 50 drops. For anything that must be accurate, such as medicine for a child, a graduated oral syringe is far more reliable than counting drops.
Infusion rate in drops per minute
The same relation underlies IV rate setting: drops per minute = (volume in mL × drop factor) ÷ time in minutes. A 1,000 mL bag over 8 hours through a 20 drop/mL set runs at 1,000 × 20 ÷ 480 = 42 drops per minute. Clinical settings use this formula with the factor printed on the giving set; the converter here handles only the volume step.
Common mistakes
- Assuming 20 drops per mL for every liquid. Alcohol-based tinctures can be 50 or more; oils 30 to 40.
- Mixing up drop factor and drops counted. The first field is what you counted; the second is the dropper’s rating.
- Trusting drops for potent medicines. Variation of ±20% between droppers is normal. Use a syringe when the dose matters.
- Dispensing too fast. Rapid drops are larger; a steady one-per-second rate matches the rated factor best.
Related tools
The volume converter moves between mL, teaspoons, fluid ounces and litres. The ounces to cups converter and litres to centilitres converter handle kitchen and lab volumes, and the mesh to micron converter covers another small-scale measurement used in labs.
External references
Frequently asked questions
How many drops are in 1 mL?
About 20 for water from a standard dropper, but anywhere from 10 to 60 depending on the dropper and liquid. Check the drop factor of your device.
How many drops in a teaspoon?
A teaspoon is 5 mL, so roughly 100 drops at 20 drops/mL.
What does gtt mean?
It is the abbreviation for drops, from the Latin gutta. Prescriptions and IV orders still use it.
Can I use this for oil-based liquids?
Yes, but change the drop factor. Most essential oil droppers give 25 to 40 drops per mL.
Does the size of the bottle change the drop size?
No, only the tip does. The same orifice reducer on a 5 mL and a 30 mL bottle gives the same drop size.