Peptide Dosage Calculator: mg & mcg to Insulin Units for Any Peptide

Every peptide dose comes down to one number: how many units do you draw on the syringe? This universal calculator gives you that for any reconstituted peptide. Enter how many milligrams are in your vial, how much bacteriostatic water you added, and your dose — in milligrams or micrograms — and it returns the exact insulin-syringe mark, the concentration you've made, and how many doses the vial holds.

The math is identical for every peptide, from a microgram-dosed nootropic to a milligram-dosed GLP-1. This page is the universal tool and the directory to our dedicated per-compound calculators, each of which adds compound-specific vial sizes, worked examples, and usage data. As the hub for the toolset, it points to the semaglutide dose calculator, the tirzepatide version, and the retatrutide tool, plus utility helpers like the reconstitution mixing calculator, the mg-to-units converter, and the reverse units-to-mg tool. Use this one to run any quick number; jump to a dedicated calculator for the full picture. Below the tool we walk through the formula, the per-peptide directory, and what real doses look like across compounds.

Key Takeaways

• One formula for every peptide: concentration = vial mg ÷ bac water mL, then units = (dose ÷ concentration) × 100 on a U-100 syringe (convert mcg to mg first).
• Anchor example: a 10 mg vial + 2 mL of bacteriostatic water = 5 mg/mL; a 0.5 mg dose is 0.1 mL = 10 units, and the vial yields 20 doses.
• mg or mcg: the calculator takes either — just pick the unit. 1 mg = 1,000 mcg, and mixing them up is a 1,000× error.
• "Units" are a volume. On a U-100 syringe, 100 units = 1 mL. The calculator turns your dose into that mark; it supports U-100, U-50, and U-40.
• Real doses span the barrel. Across our tracked compounds the median draw runs from about 4 units (microgram peptides) to 60 units (milligram peptides) — all within one syringe when mixed sensibly.
• Research compounds. Not FDA-approved; every figure is calculation context, not advice.

How does the peptide dosage calculator work?

Any peptide dose is two steps: work out the vial's concentration, then convert your dose into a volume you can read on the syringe. The units you draw are simply that volume on the insulin scale.

In plain arithmetic:

1. Concentration (mg/mL) = vial mg ÷ bac water mL. A 10 mg vial in 2 mL is 10 ÷ 2 = 5 mg/mL.
2. Volume (mL) = dose ÷ concentration. A 0.5 mg dose at 5 mg/mL is 0.5 ÷ 5 = 0.1 mL. (For a microgram dose, convert first: 500 mcg = 0.5 mg.)
3. Units = volume × 100 on a U-100 syringe (100 units = 1 mL). So 0.1 mL = 10 units.

Collapsed into the single formula the calculator runs:

units = (dose ÷ (vial mg ÷ bac water mL)) × 100 = dose × bac water mL ÷ vial mg × 100

Sanity-check our example: 0.5 × 2 ÷ 10 × 100 = 10 units. For doses per vial, divide the vial's milligrams by your dose: 10 mg ÷ 0.5 mg = 20 doses.

Our take: The one thing that trips people up across peptides isn't the formula — it's the unit. Microgram peptides (BPC-157, sermorelin, Selank) and milligram peptides (TB-500, tirzepatide, NAD+) use the same math, but a 1,000× slip between mg and mcg is the dangerous error. Pick the right unit in the toggle, and the rest is arithmetic the calculator handles.

Pick your peptide: the calculator directory

For any specific peptide, use its dedicated calculator below — each comes pre-set with that compound's real vial sizes, worked examples, doses per vial, and usage data, so you skip the setup. Use the universal tool above for anything not listed.

Each dedicated page applies the same engine as this one, so a number you get here will match the compound's own calculator for the same inputs.

Where doses land across peptides

Drawn correctly, peptide doses span the whole insulin barrel — microgram peptides sit near a few units, milligram peptides reach 50–60 units — but a sensibly mixed vial keeps every one of them inside a single syringe. This is the spread our tracked compounds show.

Because ProtocolPlus tracks reconstitutions across compounds, we can show the median units drawn per dose for each one — a useful reality check on what "normal" looks like.

The pattern is a clean split: the microgram peptides (GHK-Cu, sermorelin, BPC-157, Selank, Semax) cluster down near 4–8 units, where precision and a U-50 syringe matter; the milligram peptides (tesamorelin, tirzepatide, NAD+, MOTS-c, retatrutide, TB-500) sit mid-barrel at 40–60 units. Every one fits inside a single U-100 syringe when the vial is reconstituted sensibly.

mg, mcg, units, and syringe types

The dose is mass (mg or mcg); the units you draw are a volume; the syringe calibration sets how that volume reads. Get the unit right and pick a syringe that suits the draw size, and the calculator does the rest.

Two things to keep straight:

• mg versus mcg. 1 mg = 1,000 mcg. Microgram peptides (BPC-157, sermorelin, Selank, Semax, CJC-1295) are dosed in mcg; milligram peptides (TB-500, tirzepatide, NAD+, glutathione) in mg. Enter the dose and pick the matching unit in the toggle.
• U-100 versus U-50 versus U-40. These are syringe calibrations, and the same volume reads as a different unit count on each.

For most peptides a U-100 1 mL syringe is the default. For the microgram peptides whose draws sit under about 15 units, a U-50 spreads the mark across more readable spacing. U-40 is a rarer calibration — always confirm which barrel you're holding, since a unit means a different volume on each.

How many doses are in a vial?

Doses per vial is vial milligrams ÷ your dose — so microgram peptides give dozens of doses from a vial, while milligram peptides give only a handful. It's the other number the calculator returns, and it drives cost per dose.

The contrast is large: a 5 mg microgram-dosed peptide at 250 mcg is 20 doses, while a 10 mg milligram-dosed peptide at 5 mg is just 2. Across our tracked compounds, doses per vial runs from about 2 (TB-500) to 50 (GHK-Cu).

To turn this into money, divide the vial price by doses per vial for a true cost per dose, then by injection frequency for a weekly or monthly figure. For a full cost breakdown, see our peptide cost calculator.

A second worked example: a microgram peptide

The same formula handles a microgram-dosed peptide — you just convert the dose to milligrams (or enter mcg and let the calculator do it) before dividing by the concentration. Working one through shows why the mg/mcg toggle matters so much.

Say you have a 5 mg vial of a microgram-dosed peptide such as BPC-157, sermorelin, or Selank, and you reconstitute it with 2 mL of bacteriostatic water:

1. Concentration. 5 mg ÷ 2 mL = 2.5 mg/mL, which is the same as 2,500 mcg/mL. Keeping the vial in micrograms makes the next step read cleanly.
2. Volume. For a 250 mcg dose, 250 mcg ÷ 2,500 mcg/mL = 0.1 mL.
3. Units. 0.1 mL × 100 = 10 units on a U-100 syringe, and the vial holds 5,000 mcg ÷ 250 mcg = 20 doses.

Notice the shortcut that falls out of this: at 2,500 mcg/mL, every 25 mcg is one unit, so a 200 mcg dose is 8 units and a 300 mcg dose is 12. The key is consistency — keep the vial and the dose in the same unit family before you divide. The calculator does this automatically when you pick "mcg" in the toggle, but the most common manual error is dividing a microgram dose by a milligram concentration, which is off by a factor of 1,000. If a result ever looks absurd (a fraction of a unit, or hundreds of units for a normal dose), a mixed-up unit is almost always the cause.

These microgram draws are small — often under 15 units — so precision matters more than for a milligram peptide. A single unit of error on a 10-unit draw is 10 percent of the dose, which is why a U-50 syringe, whose marks are twice as far apart, is worth using for the smallest peptides. The dedicated per-compound calculators above flag this for each peptide, but the universal tool returns the same low-precision warning when a draw drops below about three units.

Common peptide dosing mistakes (and how the calculator prevents them)

Most dosing errors come from a handful of repeatable slips — mixing up mg and mcg, copying someone else's unit count, reading units as a dose, or using the wrong syringe — and each one shows up the same way across every peptide. Knowing them is half the battle.

• Confusing mg and mcg. The single most dangerous error, because it's a clean 1,000× miss. A "250" that should be micrograms entered as milligrams is a 1,000-fold overdose on paper. Always confirm whether your peptide is dosed in milligrams (TB-500, tirzepatide, NAD+, glutathione) or micrograms (BPC-157, sermorelin, Selank, Semax, CJC-1295), and match the toggle.
• Copying someone else's "draw X units." A unit count is only valid for one exact vial strength and water volume. The same 10-unit draw is 0.5 mg on a 5 mg/mL vial but 1 mg on a 10 mg/mL vial. If you see an instruction to "draw 20 units" online, it tells you nothing unless you also know their concentration — recalculate for your own vial.
• Reading units as a dose. Units are a volume marking on the syringe, not a measure of how much peptide you're taking. "10 units" is a tenth of a millilitre; how many milligrams that is depends entirely on your concentration.
• Not recalculating after a change. Switch vial strengths, change the water volume, or move to a different syringe, and the unit mark changes. Carrying an old number across any of those is a frequent source of error — run the calculator again whenever an input changes.
• The wrong syringe. A microgram peptide drawn on a U-100 barrel can be hard to read at 5 units; a U-50 spreads it out. A large milligram dose may not fit a small 0.5 mL barrel at all. Pick the syringe to suit the draw, and confirm the calibration (U-100 versus U-40) before you read the mark.

Because the calculator computes from your actual inputs each time, it sidesteps the copying-and-carrying errors automatically — but the mg-versus-mcg choice is yours to get right, so it's the one worth double-checking on every new peptide.

When to use this calculator versus the others

Use this universal calculator (and the per-compound pages it links to) to turn a dose into syringe units; use our other tools when your starting point is different. They share one engine, so the numbers always agree.

• This page / a per-compound calculator — you know your dose and want the units to draw. The forward, everyday tool.
• Reconstitution Calculator — you're focused on mixing a vial: how much water to add, sterile technique, and storage. The process pillar.
• mg ↔ Units Converter — you already know your concentration and just want to convert mass to units (or back), with no vial setup.
• Reverse Calculator (units → mg) — you drew a number of units and want to know how many mg or mcg that delivered.

Frequently asked questions

Sources

This is a mathematical utility. The dose-to-units conversion follows the standard U-100 insulin-syringe convention (100 units = 1 mL). Peptides covered are research compounds and are not FDA-approved; example doses are illustrative or community convention, never recommendations.

1. U-100 insulin syringe standard — 100 units = 1 mL; the basis of every unit conversion on this page.

About this guide. Written by Jordan Vance, peptide and biohacking researcher (placeholder, replace before publish), and medically reviewed by Dr. Maya Ellison, MD, biochemistry (placeholder, replace before publish), for the ProtocolPlus Research Team. This calculator and article are educational and not medical advice.