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Dose to Volume

Amount into volume

A strength off the label and an amount you already have. Out comes the volume holding it.

Educational arithmetic only. Not medical advice and not a dosing protocol.

Per millilitre of the finished solution.

Required, and not defaulted: one volume reads differently on each of these.

The answer appears here as you type.

Before you act on that number

This is educational arithmetic on figures entered by the reader. It is not medical advice, not a dosing protocol, and not a recommendation that anything be prepared, obtained or administered.

Nothing here states what quantity is appropriate for anyone, and there is no function in it that produces an amount to administer. A question about anyone’s health belongs with a licensed clinician who can examine the person asking.

Compounds of the kind this arithmetic is used on are largely research chemicals that are not approved by the FDA for human use. An exact calculation is not an accurate measurement: what is actually in a syringe depends on the preparation and the device, neither of which this page can see.

No qualified clinical reviewer is recorded against this site, and no credential is claimed anywhere on it. what this is not, at full length.

See the arithmetic
  1. The conversion is one division: volume = amount ÷ strength. Five hundred micrograms out of a 2.5 mg/mL solution is 500 ÷ 2500 = 0.2 mL, because 2.5 mg/mL is 2,500 mcg/mL.
  2. Backwards it is one multiplication: amount = volume × strength. The same 0.2 mL holds 500 mcg.
  3. The barrel reading is the volume times the calibration: units = mL × units per mL. On a U-100 that is 0.2 × 100 = 20 units; on a U-50 it is 10; on a U-40 it is 8.
  4. Both mass units are converted explicitly before anything is divided. Nothing is assumed to be in the same unit as anything else, because that assumption is how an answer ends up out by a factor of a thousand.

The strength has to come from the label, and the label is the weak point

This calculator takes the strength as given. It has no way to check it, and that is where nearly all of the real uncertainty in the answer lives: not in the division, which is exact, but in whether the number written on the vial is the number in the vial.

If the strength was itself worked out by dividing a vial mass by the diluent poured in, then it is a ceiling rather than a measurement, because the dissolved solid takes up room and the finished solution is larger than the diluent. In that case the volume this page gives you is a floor: the smallest volume that could hold the amount. Why that is a ceiling works it through, and vial into a strength is the page that computes it.

Why the syringe is a question and not an assumption

A unit is not a volume. It is a mark on one particular barrel, and the volume behind it depends entirely on that barrel's calibration. Twenty units is 0.2 mL on a U-100, 0.4 mL on a U-50 and 0.5 mL on a U-40 - the same printed number, two and a half times the liquid at the extremes.

U-100 is the most common calibration in most markets, which is exactly what makes assuming it hazardous: the assumption is right often enough to go unchecked and wrong by a large factor when it fails, and nothing about the answer would look different. So the field starts empty and the panel asks.

What this page refuses to do

It will not tell you what amount to use. There is no field on it for a person, a goal or a condition, and there is no function behind it that turns any of those into a quantity. It converts between two ways of describing an amount you had already decided on before you arrived.

That is a structural property rather than a policy. Arithmetic performed on a figure somebody else chose is a converter, and a converter cannot recommend. What this is not says the same thing at length.

Worked out already, if you would rather not type