Days Supply Calculator
Pharmacy days-supply for tablets, liquids, inhalers and insulin.
Enter your values
Tablets, mL, or units.
Results update instantly as you type — no submit needed.
Results
- Days supply
- 30 days
- Amount used per day
- 2
- Quantity for 30 days
- 60
- Quantity for 90 days
- 180
Working
- 1Per-day use = 1 × 2 = 2
- 2Days supply = 60 ÷ 2 = 30
Quick answer
Days supply = total quantity dispensed ÷ total amount used per day. For a 30-tablet bottle taken twice daily, days supply = 30 ÷ 2 = 15 days.
Days supply = quantity dispensed ÷ (dose × doses per day)
How to use the Days Supply Calculator
- 1Enter the quantity dispensed.
- 2Enter the dose size and how many times a day it is taken.
- 3Read the days supply and the 30/90-day quantities.
Frequently asked questions
How do you calculate days supply for insulin?
Add up the total units used per day across all injections, then divide the total units dispensed (for example 1000 units in a box of five 3 mL pens at 100 units/mL) by that daily total.
Do you round days supply up or down?
Insurers almost always require rounding down to whole days, so a 15.6-day calculation is billed as 15 days.