Prescription Countdown Calculator

Enter your remaining grams, typical daily use, and days until your next prescription fill to see how long your supply will last and whether you will make it.

Grams remainingHow many grams you have on hand right now.

Estimated daily use (g)Your average grams per day. Use an estimate.

Days until next prescriptionHow many days until your prescription renews.

Enter your remaining grams, daily use, and days until your next prescription to see your countdown.

How it works

This calculator estimates how long your current supply will last based on your typical daily use. It then compares that to how many days remain until your next prescription date.

The calculation: divide your remaining grams by your daily use to get the number of days until you run out. Then compare that to the days until your next prescription fill. If your supply lasts at least as long as the wait, you are in good shape.

Remember: this is an estimate. Your actual daily use may vary, and the calculator does not account for missed doses, unlogged consumption, or changes in your prescription.

Disclaimer: This calculator provides estimates only. It does not constitute medical advice, dosing guidance, or a guarantee of supply. Always consult your prescriber about your medication.

Tired of doing the maths yourself?

Grams Left updates your countdown automatically with every dose you log. No more manual calculations -- just set what you have and log what you use.

Start tracking free →