Dosage Calculations Calculator
Dosage calculations calculator works out Dose and Volume to give from What to calculate, Dose wanted (desired) and Dose unit. The default figures on this page give volume to give of 2.500 mL; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
2 steps
- Concentration = 500 mg / 5 mL = 100 mg/mL
- Volume = dose / concentration = 250 mg / 100 mg/mL = 2.5 mL
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
5 sources
What the dosage calculations calculator calculates
Converts between drug mass, solution concentration and volume: desired-over-have, mg to mL, mg/kg and mg/m² dosing, reconstitution, tablets per dose, days supply, mg/kg maximum dose and titration schedules.
How to use this dosage calculations calculator
Enter What to calculate, Dose wanted (desired), Dose unit and Strength on hand (have). Dose updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Dose, Volume to give and Concentration.
The method follows United States Pharmacopeia, General Notices 8.140 - percentage concentrations: % w/v is grams of constituent per 100 mL of solution, Mosteller RD. Simplified calculation of body-surface area. N Engl J Med 1987;317:1098, Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med 1916;17:863-871, MOUNJARO (tirzepatide) injection - FDA prescribing information, section 2 Dosage and Administration and NIST Special Publication 811 - exact unit conversions used for mass and volume.
Desired over have: 250 mg from 500 mg in 5 mL example
With What to calculate: desired-over-have, Dose wanted (desired): 250, Strength on hand (have): 500, Volume that strength is in (quantity): 5, the calculator returns Volume to give: 2.5, Concentration: 100, Dose: 250. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Dose, Volume to give and Concentration. The inputs you can vary are What to calculate, Dose wanted (desired), Dose unit, Strength on hand (have), Strength unit and Volume that strength is in (quantity).
Understanding Dose, Volume to give and Concentration
Educational calculation only. Always verify every dose against the product label and your institution's policy before administering a medicine.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
What information do I need for the dosage calculations calculator?
You need What to calculate, Dose wanted (desired), Dose unit, Strength on hand (have), Strength unit, Volume that strength is in (quantity), Stock volume unit and Volume given. The page opens with default figures that give volume to give of 2.500 mL, so you can see the scale before entering your own.
What does this dosage calculations calculator show?
It shows Dose, Volume to give, Concentration, Tablets per dose, Total daily dose, Body surface area, Final volume after reconstitution and Days supply, with the working and any warnings for your entries.
Can I check how the dosage calculations calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.