Prescription Refill Calculator

Created by Łucja Zaborowska, MD, PhD candidate
Reviewed by Anna Szczepanek, PhD and Adena Benn
Last updated: Nov 03, 2022

The prescription refill calculator relieves you from the mundane task of computing days supply and the amount of medicine needed for a given therapy. It will also relieve you from the next refill date calculations. 💊

Dig into our prescription refill calendar and make your life a little bit easier!

Ps. If you wish to perform more complicated dosage calculations, visit our dosage calculator or the pediatric dose calculator.

How to calculate day supply for liquids?

Day supply for liquids calculations? Let's break it down.

  1. Find out the total volume of your drug.
  2. Look at your prescription.
    • Find out how often you take the drug.
    • Learn what's the amount you need to take for a single dose.

If your single dose amount is in volume, proceed to step 4.

  1. If your amount is given in mg.

    • Get to know your drug's concentration and calculate your dose volume:

    Dose volume = Dose(mg) / Concentration(mg/mL)

  2. Finally, use the equation:

    Days supply = Total volume / (Dose volume × Frequency)

Rx refill calculator vs OTC refill calculator

Let's explain the main difference between Rx drugs and OTC drugs.

  • OTC stands for the over-the-counter - it means that the drug in question is easily accessible, there are no restrictions, and the pharmacy will sell it to everyone. However, the OTC label doesn't mean that the drug is entirely harmless, and you can take it without any precautions!

  • Rx means prescription drug that a doctor must prescribe for a specific patient and a selected disease. These drugs are usually stronger than OTC medicines and may pose a greater risk to a patient if misused.

Both types of drugs can be taken regularly and may require a refill - the Rx drugs are more difficult to obtain because of a required consultation with a doctor.

How to calculate day supply for tablets?

The day supply calculations for tablets are relatively easy to compute. Let's get down to it:

  1. Find out the total number of tablets you have.
    Add the number of tablets from all the packages you got.

  2. Check your prescription/instructions.

    • Find out how often you need to take your medicine, e.g., once a day.
    • Discover how many tablets you need to take for a single dose.
  3. Use the following equation:

    Days supply = Total no. of tablets /(Tablets per dose × Frequency)

💡 Looking for tools dedicated to a specific medication? Start with levothyroxine dosage calculator or the adderall dosage calculator!

How to use the medication refill calculator?

The medicine refill calculator allows you to perform three different kinds of pill refill calculations:

  • Next refill date;
  • Expected days supply of tablets; and
  • Expected days supply of liquid drugs.
  1. Choose the section of your interest - Refill date or Days supply.
    • If you chose the Days supply, choose whether your drug's liquid or in the form of tablets/capsules.
  2. Each of the variants requires specific input:
    • Refill date: fill date and days supply;
    • Days supply: the total amount of the drug, required dosage, and frequency.
  3. Once you have added these values, our calculator will tell you the length of time your medication will last.
  4. Our tool works both ways. It could calculate the length of time your medication will last or, given a specific time(expected supply), dosage, and frequency, it would return the amount of medication you need. Do not hesitate to play with it a little!

FAQ

How to perform 30 day prescription refill calculations?

It just couldn't be easier!

  1. Write down the date of your first dose.
  2. Add 29 days to the date you've just written.
  3. Obtained date is the last dose of your medication.
  4. The next refill period should begin the day after this date (+30 days).

Always remember that the number of days in each month may vary!

How to perform 90 day prescription refill calculations?

Let's make it nice and simple:

  1. Remember the date of your first dose.

  2. Add 89 days to the date you've just written.

    Last dose date = First dose date + 89 days

  3. Calculated date marks the last dose of your medication.

  4. The next refill period should begin the day after this date (+90 days).

Always remember that the number of days differs from month to month.

How to perform 28 day prescription refill calculations?

28 days equal 4 weeks - this calculation is probably the easiest to perform with the use of the calendar!

  1. Find out the date of your first dose.

  2. Use the equation below:

    Last dose date = First dose date + 27 days

  3. You've just calculated your last dose date. Your next refill period should start a day after that (+28 days).

*Always remember that the number of days varies from month to month.

Łucja Zaborowska, MD, PhD candidate
Refill date
Fill date
Days supply
days
Next refill
Days supply
Drug type
Tablets / capsules
Total number of tablets
#
Dosage
tablets/dose
Taken
once per day
Expected supply
days
Check out 23 similar dosage calculators 💊
Adderall dosageAleve dosageBenadryl… 20 more
People also viewed…

CURB-65

Thanks to CURB-65 calculator you can decide whether the patient with community-acquired pneumonia should be treated in the hospital or in outpatient!

Meat footprint

Check out the meat impact - on the environment and your health.

Opioid conversion

The opioid conversion calculator tells you equivalent doses of analgesic drugs, such as morphine, fentanyl, or tramadol.

Podcasts

Do you feel like you could be doing something more productive or educational while on a bus? Or while cleaning the house? Well, why don't you dive into the rich world of podcasts! With this podcast calculator, we'll work out just how many great interviews or fascinating stories you can go through by reclaiming your 'dead time'!
Copyright by Omni Calculator sp. z o.o.
Privacy policy & cookies
main background