Eye Drop Supply Calculator
Last reviewed: July 2026
Use this eye drop supply calculator to estimate how long an eye drop bottle may last. Enter the bottle size, estimated drops per mL, drops per dose, eyes treated, and doses per day to estimate total drops and days supply.
This is a planning and education tool only, not dosing or medical advice.
Enter eye drop details
Common estimate: 20 drops/mL.
Some bottles may need priming drops before first use.
Enter a date to estimate run-out date.
Estimated days supply
100 drops
4 drops
25 days
How do you calculate eye drop days supply?
Estimate total drops by multiplying the bottle size in mL by the drops per mL. Estimate drops used per day by multiplying drops per dose, eyes treated, and doses per day.
Divide total drops by drops used per day to estimate days supply. For example, about 100 total drops divided by 1 drop per day equals about 100 days.
The result is an estimate because actual drop size, bottle design, priming, waste, and prescription directions may differ. This is basic math for planning purposes only.
Eye drop days supply formula
Total drops = bottle size in mL x drops per mL
Drops used per day = drops per dose x eyes treated x doses per day
Days supply = total drops / drops used per day
- 5 mL x 20 drops/mL = about 100 drops
- 1 drop in 1 eye once daily = 1 drop/day
- 100 drops / 1 drop/day = about 100 days
- 1 drop in both eyes twice daily = 4 drops/day
- 100 drops / 4 drops/day = about 25 days
Eye drop days supply examples
| Bottle size | Drops per mL | Use entered | Estimated days supply |
|---|---|---|---|
| 2.5 mL | 20 drops/mL | 1 drop in 1 eye once daily | about 50 days |
| 5 mL | 20 drops/mL | 1 drop in 1 eye once daily | about 100 days |
| 5 mL | 20 drops/mL | 1 drop in both eyes once daily | about 50 days |
| 5 mL | 20 drops/mL | 1 drop in both eyes twice daily | about 25 days |
| 10 mL | 20 drops/mL | 1 drop in both eyes twice daily | about 50 days |
These examples are for math planning only. Actual days supply can vary by drop size, bottle design, priming, waste, medication directions, and pharmacy or insurance calculation methods.
Eye drop supply examples
Example 1: 5 mL bottle, 20 drops/mL, 1 drop in 1 eye once daily — 5 x 20 = about 100 total drops. 1 drop per day means the bottle may last about 100 days.
Example 2: 5 mL bottle, 20 drops/mL, 1 drop in both eyes twice daily — 1 drop x 2 eyes x 2 times per day = 4 drops per day. 100 / 4 = about 25 days.
Example 3: 10 mL bottle, 20 drops/mL, 1 drop in both eyes twice daily — 10 x 20 = about 200 total drops. 200 / 4 = about 50 days.
Why your eye drop supply may be different
Related refill calculators
What this eye drop calculator cannot tell you
Eye drop supply FAQ
How do I calculate days supply for eye drops?+
Multiply the bottle size in mL by drops per mL to estimate total drops. Multiply drops per dose, eyes treated, and doses per day to estimate drops used per day. Then divide total drops by drops used per day.
How many drops are in 1 mL of eye drops?+
A common estimate is about 20 drops per mL for standard aqueous eye drops. The actual number can vary by bottle design, drop size, and solution thickness.
How many drops are in a 5 mL eye drop bottle?+
At an estimated 20 drops per mL, a 5 mL bottle contains about 100 drops. This is a math estimate; actual drops may vary by bottle design and drop size.
How long should a 5 mL eye drop bottle last?+
Using 20 drops per mL as an estimate, a 5 mL bottle has about 100 drops. At 1 drop in 1 eye once daily, the supply may last about 100 days. At 1 drop in both eyes twice daily, about 25 days. Actual days supply may differ.
How long should a 10 mL eye drop bottle last?+
Using 20 drops per mL as an estimate, a 10 mL bottle has about 200 drops. At 1 drop in both eyes twice daily, that is about 4 drops per day, so the bottle may last about 50 days by basic math.
Why does my pharmacy eye drop days supply differ from my estimate?+
Differences may happen because of bottle design, actual drop size, priming or wasted drops, one-eye versus both-eyes directions, dose changes, or pharmacy and insurance system calculation methods.
What if I use drops in both eyes?+
Enter 2 for the eyes treated field. The calculator multiplies drops per dose by both eyes and doses per day to estimate total drops used daily.
What if I use eye drops more than once per day?+
Enter the number of times per day in the doses per day field. The calculator multiplies drops per dose, eyes treated, and doses per day to estimate daily drop use.
Can this calculator tell me when I can refill eye drops?+
No. This calculator estimates days supply, not refill dates. For refill-date math, use the Prescription Refill Date Calculator. Actual refill timing depends on your pharmacy, insurance plan, prescriber, medication, and local rules.
Should I ask my pharmacist or eye doctor if the estimate looks wrong?+
Yes. If the estimated days supply differs from what you expect, ask your pharmacist, prescriber, or eye care professional. You can also review the Medical Disclaimer.
About this eye drop supply calculator
This calculator uses basic bottle-size and drop-count math to estimate eye drop days supply from the numbers entered. It is designed for planning and education only. It is not medical, dosing, legal, insurance, or dispensing advice.
Related resource: Eye Drop Days Supply Chart — A printable chart with estimated days supply for common eye drop bottle sizes and usage patterns.