Pharmacist Tool
Eye Drops Days Supply Calculator
Calculate ophthalmic days supply using bottle size, drops per mL, dosing frequency, and one-eye or both-eyes directions.
Free eye drops days supply calculator for pharmacists and pharmacy technicians. Estimate ophthalmic day supply using bottle size, drops per mL, drops per dose, dosing frequency, and one-eye or both-eyes use. This eye drop days supply calculator helps pharmacists calculate ophthalmic days supply using bottle size, drops per mL, and dosing frequency.
Calculator inputs
Loading FDA eye-drop data…
Default workflow value is 20 drops per mL.
Enter 0 for an eye that is not being treated.
Results
Total drops
—
Drops used per day
4
Estimated days supply
—
Rounded down whole days
—
Formula used
Days Supply = Total Drops in Bottle ÷ Drops Used Per Day
Total Drops = bottle count × bottle size (mL) × drops per mL
Drops Used Per Day = (left eye drops + right eye drops) × times per day
Notes for pharmacy workflow
Common eye drop examples
Need a drug-specific example? These pages show how days supply can be estimated for common ophthalmic prescriptions and then linked back to the main calculator.
Latanoprost days supply calculator
Example calculations for latanoprost eye drop prescriptions.
Timolol days supply calculator
Step-by-step timolol ophthalmic day supply workflow example.
Brimonidine days supply calculator
Drug-specific guide for brimonidine eye drop day supply.
General eye drop days supply guide
Learn the formula and workflow behind ophthalmic day supply calculations.
How eye drops days supply is calculated
Eye drops days supply is generally calculated by estimating the total number of drops in the dispensed bottles and dividing that total by the number of drops used per day. Pharmacists often estimate drops per mL because bottle design and solution characteristics can vary.
Days Supply = Total Drops ÷ Drops Used Per DayIn pharmacy workflow, the final practical supply can vary depending on one-eye versus both-eyes directions, drops per administration, administrations per day, and the estimated drops per mL used for the calculation.
Learn how to calculate eye drop days supply →Why pharmacists use an eye drops days supply calculator
Frequently asked questions
How do you calculate eye drop days supply?
Eye drop days supply is calculated by estimating the total drops available in the dispensed bottles and dividing by the number of drops used per day.
How many drops are in 1 mL of eye drops?
A common pharmacy workflow estimate is 20 drops per mL, although real-world values can vary depending on bottle design and product characteristics.
Why can eye drops days supply vary?
Eye drops days supply can vary because drops per mL are estimated, patient technique varies, and one-eye versus both-eyes directions change the daily number of drops used.
More ophthalmic guidance
Need help with the calculation method? Visit the eye drop days supply guide for a step-by-step explanation.
Also calculating otic prescriptions? Use the ear drop days supply calculator.
Important note
Always use professional judgment and follow product labeling, payer requirements, and pharmacy workflow policies when determining billed days supply.