Convert drops to millilitres and millilitres to drops using a standard dropper or an IV giving set's drop factor.
mL = drops ÷ drops per mL
The drop factor of an IV set is printed on its packaging.
Drop sizes vary between droppers and liquids, so drops are an estimate, not a dose measurement. For any medicine, follow the instructions on the label or from your pharmacist, and use the dropper, oral syringe or measuring device supplied with it.
IV drip rates should be set and checked according to your facility's protocol. This page explains the arithmetic and doesn't replace clinical guidance.
Every conversion depends on how many drops make one millilitre, called the drop factor. With a standard dropper that delivers 20 drops of water per mL, each drop is 0.05 mL.
Example: 30 drops from a 20 drops/mL dropper = 30 ÷ 20 = 1.5 mL.
IV sets have a stated drop factor. The other rows are typical ranges, so check the product if accuracy matters.
| Device or liquid | Drops per mL | mL per drop |
|---|---|---|
| Standard medicine dropper (water) | 20 | 0.05 |
| IV macrodrip set | 10, 15 or 20 | 0.1, 0.067 or 0.05 |
| IV microdrip (paediatric) set | 60 | 0.017 |
| Eye drop bottle | about 20–40 | about 0.025–0.05 |
| Alcohol tincture or essential oil | often 30+ | under 0.035 |
1,000 mL of fluid is to run over 8 hours through a gravity giving set with a drop factor of 15 drops/mL. How many drops per minute?
Step 1: Convert the time to minutes
Step 2: Apply the formula
About 31 drops per minute. With a 60 drops/mL microdrip set, the drops per minute always equal the mL per hour. Here that's 125, which is why microdrip sets are easy to set by eye.
A 5 mL bottle of eye drops delivers drops of about 0.04 mL. You use one drop in each eye, twice a day.
Step 1: Drops in the bottle
Step 2: Days of use
Roughly a month, less any drops that miss. The leaflet usually says how long the bottle can be used once opened, and that limit applies even if drops remain.
About 20 drops of water from a standard dropper. IV sets are made to deliver exactly their stated drop factor: 10, 15, 20 or 60 drops per mL.
About 100 drops of water at 20 drops per mL, since a teaspoon is about 4.93 mL. Don't use a kitchen teaspoon for medicine. Use the measuring device supplied.
Oils and alcohol-based liquids have lower surface tension than water, so their drops are smaller. Many give 30 or more drops per mL.
An IV set with a fine tip delivering 60 drops per mL, used when small, precise volumes are needed, such as for children. At 60 drops/mL, drops per minute equal mL per hour.
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