Days Supply Calculator
Days supply for tablets, liquids, insulin pens, inhalers and eye drops.
Open the tool → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Dosage form
- Insulin pen or vial
- Insulin: units per mL
- 100
- Insulin: mL per pen or vial
- 3
- Insulin: pens or vials dispensed
- 1
- Insulin: units injected per day
- 8
- Insulin: injections per day
- 1
- Insulin: priming units per injection
- 2
- In-use discard limit in days, if the label gives one
- 28
Result: 28-day supply: 300 units ÷ (8 units + 2 priming × 1 injection a day) = 30 days, capped at 28 by the 28-day in-use discard limit.
The tool opens with these values already filled in. Replace them with your own.
What you enter
- Dosage form
- Tablets or capsules: quantity dispensed
- Tablets or capsules: units per dose
- Liquid or drops: volume dispensed (mL)
- Liquid: dose volume (mL)
- Insulin: units per mL
- Insulin: mL per pen or vial
- Insulin: pens or vials dispensed
The other 17 fields
- Insulin: units injected per day
- Insulin: injections per day
- Insulin: priming units per injection (from the label)
- Inhaler: actuations per canister
- Inhaler: canisters dispensed
- Inhaler: puffs per dose
- Drops: drops per mL (manufacturer or plan figure)
- Drops: drops per eye per dose
- Drops: eyes treated
- Doses per day (all forms but insulin)
- In-use discard limit in days, if the label gives one
- Inhaler: priming puffs per canister (optional)
- Inhaler: doses left on the counter (optional)
- As-needed sig: is the daily use entered the maximum allowed?
- Start date of the supply (YYYY-MM-DD, optional, for a run-out date)
- Trip: departure date (YYYY-MM-DD, optional)
- Trip: return date (YYYY-MM-DD, optional)
How this is calculated
Citation
Arithmetic on the label and the prescription: usable quantity divided by daily use, rounded down, capped by the label's in-use discard limit. No federal source gives a drops-per-mL figure; the reader supplies it. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.