DocTayo Pharmacy Calculation Tool

Eye-Drop Days' Supply Calculator

Calculate one-eye or both-eye use for multidose bottles, PRN directions, fixed courses, tapers, and single-use containers.

State the assumption. The default is 20 drops per mL, but actual bottle yield varies. Use the payer's or pharmacy's approved factor and verify the exact NDC, package, discard date, and prescribed laterality.

Enter the prescription

Calculation result

Days' supply - Enter the prescription and calculate.
Formula: estimated drops supplied / daily drops used

Drop-factor sensitivity

-15 drops/mL
-20 drops/mL
-25 drops/mL

Interpretation

The result will identify the assumption and whether the quantity covers a fixed course or taper.

Calculation cautions

  • Twenty drops per mL is a convention, not a measured constant. Commercial bottle yield varies.
  • "Affected eye(s)" may require clarification before choosing one or two eyes.
  • For fixed courses, the treatment duration may be the appropriate days' supply when the quantity is sufficient.
  • For PRN directions, the shortest interval or labeled daily maximum produces a maximum-use estimate.
  • Single-use products should be calculated by containers when the container must be discarded after one administration.
  • Manufacturer discard dates and compounded beyond-use dates can limit the usable period even when volume remains.