Peptide dose calculator

A dose calculator answers a single question: given a vial that has already been reconstituted, how many units do I need to draw to deliver a specific dose? It is the everyday tool — the one used multiple times a week — once a vial is set up. The reconstitution math happens once. The dose math happens every single injection.

The inputs are simple. You type the milligrams of peptide originally in the vial, the millilitres of bacteriostatic water you added, and the dose you want to deliver. The calculator derives the concentration in the background and converts your dose into both a millilitre volume and an insulin-syringe unit count. You only ever need to look at the unit count when actually drawing.

The reason this calculator exists separately from the reconstitution calculator is workflow. The reconstitution calculator is framed around setting up a new vial, which includes doses-per-vial. The dose calculator is framed around a single injection — what to draw right now — and stays out of the way of the larger inventory question.

A typical peptide dose lands somewhere between 0.05 and 0.5 millilitres of solution. Reading those volumes accurately on a tuberculin syringe is hard, because the markings are sparse and a small visual error becomes a large percentage error. Insulin syringes were designed for the opposite problem — measuring very small volumes very precisely — which is why they have become the default for peptide use.

When the calculator says you need to draw 12 units, it means you pull the plunger to the line marked 12 on a U-100 insulin syringe. That is exactly 0.12 millilitres of solution, which contains exactly the dose you typed in, given the concentration of the vial you described. The number you read on the syringe is the number the calculator returns.

The conversion only works when the syringe is a standard U-100. U-40 syringes — common in veterinary contexts — use a different scale, and treating one as the other will produce a dose that is off by a factor of 2.5. This calculator assumes U-100, which is what nearly every peptide user is actually using.

Some peptides are typically discussed in micrograms — for example, BPC-157 protocols often specify a dose of 250 mcg rather than 0.25 mg, even though those are exactly the same amount. The mg-mcg toggle on the calculator exists so you can type the dose in whichever unit the vial label or the protocol you are following uses, without having to do mental decimal-place conversion.

Misplacing a decimal between mg and mcg is one of the most common errors in peptide preparation, because the difference between 0.25 mg and 25 mg is a factor of 100. The calculator handles the conversion internally and shows you the unit draw in real time, which makes a typo immediately obvious — a 100x error produces an absurd unit count rather than a quietly wrong dose.

If you reorder the same peptide at the same vial size and reconstitute it with the same diluent volume, the unit-per-dose number stays identical. You can keep using the same draw count without re-running the calculator. That is most of the value of writing the unit count down somewhere permanent the first time around.

If anything changes — vial size, diluent volume, or the dose itself — the unit count changes. A 10 mg vial reconstituted with 2 mL of BAC water has a different concentration from a 5 mg vial reconstituted with 2 mL, even though both look the same in the syringe. The dose calculator is the fastest way to re-derive the unit count when any input shifts.

Logging vials and doses in a dedicated app instead of in your head removes the error path entirely: the vial is recorded once with its full set of inputs, and every subsequent dose entry is calculated against that specific vial. When the vial is finished and a new one is started, the new vial's inputs are entered fresh and the old draw count is retired.

Most U-100 insulin syringes are graduated in 2-unit increments, which means any value the dose calculator returns has to be rounded to the nearest visible mark. A computed 7.4 units is drawn as either 6 or 8 in practice — there is no half-mark to aim at. The good news is that small rounding shifts produce only small mass shifts, well inside the natural variability of any weekly protocol.

If you find yourself constantly rounding because your typical dose lands at only 2 or 3 units, that is a strong signal to reconstitute the next vial at a lower concentration. Doubling the diluent volume halves the concentration and doubles the unit count, which gives you twice the resolution on the syringe without changing the actual mass delivered.

Air bubbles cause the other common reading error. A small bubble at the top of the syringe shifts the meniscus by a few units worth of volume, quietly under-delivering every dose. Tap the barrel sharply with the needle pointing up to send any bubble to the top, then expel until liquid appears at the needle tip and re-read the unit mark before injecting.

For protocols dosed once or twice a week, the dose calculator is usually only opened the first time a vial is set up. The unit count is identical on every subsequent injection from that vial, so writing it on the vial label or saving it in a tracking app turns every future shot into reading a number rather than recomputing it.

For protocols dosed daily — or for people running multiple peptides side by side — the calculator becomes more of a daily reference. In that case, the friction of opening a calculator app every day quickly outpaces the friction of using a tracker that pre-computes the unit count for each scheduled dose. Either workflow is valid, but they trade off in different directions.

When the dose itself changes mid-protocol, the dose calculator is the cleanest way to re-derive the new unit count without re-typing the vial inputs. Saving both the old and new dose entries in a log keeps a clean record of when the change took place, which matters more than most people realise when reviewing a protocol weeks later.