Dosage Calculator
16 calculators for the arithmetic between a prescribed dose and what actually gets given. Each one shows the formula, the numbers put into it and the result.
- Free, no sign-in
- Evidence-based formulas
- Working shown
400 mg prescribed, at a strength of 250 mg in 5 mL
8 mL
Every calculator
Dose and volume
What to draw up, once the strength on the label is known.
Working out the dose
Weight-based orders and countable tablets.
Infusions
Pump rates, gravity drip rates and how long a bag runs.
Clinical calculations
Renal function, body measures and lab corrections.
- Creatinine clearanceCockcroft-Gault, with the weight the estimate used shown.
- eGFRCKD-EPI 2021, the race-free equation.
- Body surface areaMosteller, Du Bois, Haycock and Gehan, side by side.
- Ideal body weightDevine, Robinson, Miller and Hamwi, plus adjusted body weight.
- Corrected calciumWhat the total calcium would read at a normal albumin.
- Anion gapWith or without potassium, and corrected for albumin.
Built to be checked
The working, on every result
The formula, the numbers put into it and each step, so the answer can be checked rather than trusted.
Every formula cited
Named equations carry the paper they came from and the date it was read, under the result and on the formulas page.
Nothing stored, nothing to sign
It runs in your browser. No account, no paywall, and nothing you type is sent anywhere.
What a dosage calculation actually is
Almost every calculation on this site is one division standing between two numbers that were measured in different things. A dose is an amount of medicine. What gets given is an amount of liquid, a count of tablets or a rate on a pump. The number that bridges the two is always printed somewhere on the product.
For a liquid, that bridge is the strength. A 250 mg in 5 mL suspension holds 50 mg in every millilitre, so a 400 mg dose is 8 mL. Change the product to a 125 mg in 5 mL suspension and the same order becomes 16 mL, twice the liquid for the identical dose. That is the point the mg to mL calculator is built around.
For an infusion the bridge is the same idea moving in time: the strength of the made-up bag turns a dose rate into a pump rate. For a weight-based order it arrives a step earlier, because the dose itself does not exist until a weight is known.
Which calculator you need
If you have a dose and a bottle, you want a volume, which is themg to mL calculator. If the two are written in different units, themcg to mg converter gets them onto the same ladder first.
If the order is written per kilogram, the dose has to be worked out before anything can be measured, and whether the figure is a single dose or a daily total changes it several times over. That distinction is what the mg/kg calculator keeps in front of you.
If a bag is running, you want either a rate or a time. The IV flow rate calculatorgives millilitres an hour for a pump, the drip rate calculator gives drops a minute for a gravity line, and the infusion time calculator answers the question the other way round.
The clinical calculators sit apart from all of that. Renal function, body surface area and the lab corrections do not produce a dose; they produce a figure that a dosing table or a protocol then asks for. Every one of them names the equation it used and links to where that equation was published, which is collected on theformulas page.