Peptide Insider

Peptide Calculator

How the calculation works

Four relationships do all the work here, and not one of them is an estimate. They are definitions, so they hold for every compound and every vial.

Concentration is the peptide in the vial divided by the water you added. Ten milligrams in two millilitres is five milligrams per millilitre. The lyophilised powder adds no volume worth counting, so the water you measure is the volume you get.

Volume per dose is your dose divided by that concentration. At five milligrams per millilitre, a two milligram dose sits in 0.4 mL.

Syringe units convert that volume into the marks printed on the barrel. A U-100 insulin syringe is graduated so that one unit is exactly 0.01 mL, which makes 0.4 mL exactly 40 units. The unit is a volume, not an amount of peptide.

Doses in the vial is the vial strength divided by the dose, and it has nothing to do with the water. Ten milligrams at two milligrams a dose is five doses whether you reconstituted with one millilitre or three.

Water changes the reading, not the amount

This is the part that trips people up. Adding more bacteriostatic water does not dilute the peptide you draw, it only spreads the same peptide across a longer stretch of the barrel. The dose is unchanged; the number of units you pull to reach it goes up.

That is useful in both directions. If a dose works out at one unit, the mark is too small to read and a small hand tremor becomes a large percentage error, so more water makes the same dose easier to measure. If a dose works out at more than a hundred units it will not fit in one syringe, and less water fixes it.

U-100 and U-40 are not interchangeable

A U-100 syringe puts 100 units in a millilitre. A U-40 syringe puts 40. The same 0.08 mL is eight units on one and 3.2 units on the other, so reading a U-100 number off a U-40 barrel overdoses by two and a half times, and the reverse underdoses by the same factor.

U-40 syringes are mostly veterinary and are easy to end up with by accident. The calculator has an explicit switch rather than assuming, and the result is always labelled with the syringe it belongs to. Check the barrel before you trust any number, including ours.

When the calculator flags something

Four situations produce a warning. None of them stops the calculation, because the arithmetic is still correct — they mark a result that is awkward or impossible to act on.

More than one millilitre. A standard insulin syringe holds 1 mL, so anything above that needs either a second draw or a more concentrated solution.

Under two units. Below roughly two units you are reading between marks and guessing. More water gives the same dose a larger, readable volume.

Dose larger than the vial. Almost always a units mistake — micrograms entered as milligrams, or the other way round.

More than five millilitres of water. Many vials physically will not take it. Check there is room before you push the plunger.

What this calculator will not do

It will not suggest a dose, a frequency or a schedule, and it will not fill anything in for you beyond a starting water volume that you are meant to replace. There are no approved dosing instructions for most of the compounds indexed on this site, which means there is no source anyone could honestly cite. What circulates on forums and vendor pages is other people guessing, and repeating a guess in a calculator would only make it look authoritative.

Peptide Insider indexes what vendors publish about the material they ship and what it costs per milligram. We do not sell peptides and we do not advise on their use. The arithmetic above is arithmetic. Nothing on this page is medical advice.

Where the vial sizes come from

The quick-pick buttons under the vial field are not a hand-kept list. They are the vial sizes vendors in our index actually publish, read from the same data behind the price comparison and the vendor tables. When a vendor changes what they stock, the buttons change with them.

For compounds we do not index there are no buttons, and you type what is printed on your own vial. We would rather show nothing than invent a number.

Compound-specific dosage calculators

The same reconstitution arithmetic, set next to what each compound’s human trials actually administered (or the plain statement that none exist). Every calculator converts only the figures you enter and never suggests a dose.

Common questions

How much bacteriostatic water should I add?

That is your decision, and this site does not recommend a volume. What matters is that the water changes only how far the same amount of peptide is spread along the syringe barrel, not how much peptide a dose contains. Enter whatever you actually added and the calculator will tell you what the reading becomes.

Does adding more water make the dose weaker?

No. A dose is an amount of peptide, and that amount is fixed by what you draw, not by the concentration. More water lowers the concentration, so the same dose occupies a larger volume and more units on the barrel. The peptide going in is identical.

What is a unit on an insulin syringe?

A unit is a volume, not an amount of drug. On a U-100 syringe one unit is 0.01 mL, so a hundred units fill one millilitre. That is why the same solution reads as a different number of units on a different syringe.

How do I tell a U-100 syringe from a U-40 one?

It is printed on the barrel and on the packaging. The difference matters: U-40 puts 40 units in a millilitre instead of 100, so reading a U-100 figure off a U-40 barrel delivers two and a half times the intended volume. The calculator has an explicit switch rather than assuming, and every result is labelled with the syringe it belongs to.

How many doses will one vial give me?

The vial strength divided by your dose. It does not depend on how much water you added: ten milligrams at two milligrams a dose is five doses whether you reconstituted with one millilitre or three. Water changes the reading, not the arithmetic of how much peptide is in the vial.

Does this calculator tell me what dose to use?

No. It converts figures you enter and suggests nothing. There are no approved dosing instructions for most of the compounds indexed on this site, so there is no source anyone could honestly cite, and repeating what circulates on forums would only make a guess look authoritative.

Why does my result show a warning?

Four situations get flagged, and none of them stops the calculation. A volume above one millilitre will not fit in a single insulin syringe. A reading under two units is too small to measure reliably. A dose larger than the whole vial is almost always a micrograms-for-milligrams mistake. More than five millilitres of water may not physically fit in the vial.