Peptide math 'splained without the science degree. Enter your own values to explore concentration, liquid volume, and syringe-scale equivalents—with the math shown.
Use the total mass shown on the vial label, not mg/mL.
This calculation assumes final solution volume equals liquid added. Actual final volume may differ.
This tool never chooses, recommends or validates a dose.
Enter the number shown on the volume scale, not a medication dose.
Check your actual syringe. Tick spacing varies by product; the size alone does not establish the spacing.
Fill in the fields to see the math update instantly.
Enter all required numbers above to see each conversion.
They measure the same thing (how much material there is), just in very different-sized units.
mg means milligram. mcg means microgram. A microgram is 1,000 times smaller than a milligram—so the very same amount has a number that's 1,000 times bigger when written in mcg.
Type a number to see the same quantity in the other unit. This is only a mass-unit conversion.
mg → mcg: multiply by 1,000.
Why this matters: Mixing up mg and mcg makes a 1,000-fold difference. For example, 1 mg is not 1 mcg. Always double-check the unit printed next to a number; a correct conversion does not tell you whether an amount is medically appropriate.
These are measures of mass. Think of them as two ways of labeling the same quantity, like grams and smaller fractions of a gram.
Milliliters measure liquid volume—not the mass of the substance in it. To connect mass and volume, you also need the concentration (mg/mL).
These are volume markings, not mg or mcg. On a U-100 scale, 100 marked units equal 1 mL. The concentration determines how much material is in that volume.
Learn which numbers mean mass, liquid volume, or marked scale positions.
What's a milligram? What's a microgram? Why does the number change by 1,000?
Learn the basics →GUIDE 02Understand the difference between milliliters, syringe markings, and substance mass.
Understand the scale →HOW IT WORKSReview the assumptions, arithmetic, rounding and warnings behind the calculator.
Our methodology →Science and policy move fast. Our companion publication will cover peptide research, regulatory developments, and important news—with sources and clear editorial disclosures.
All calculator arithmetic is performed in your browser, and entered numbers are not sent to PepSplain for calculation. We use Cloudflare Web Analytics and a privacy-limited Google Analytics 4 setup for site traffic, navigation and engagement measurement; analytics events do not include calculator values or entered amounts. See our privacy policy. The formulas are:
Results may be rounded for display. The number of full portions is theoretical only and ignores losses, residual volume and product-specific factors. An arithmetic or tick-alignment check does not establish medical safety or measuring accuracy.
Read the full methodology, limitations, and worked examples →
Peptide math 'splained without the science degree. PepSplain is a standalone educational calculator and a set of plain-English measurement guides. We show the calculation, its assumptions and its limitations. This is not a tool for selecting medications, substances or amounts for use.
Ownership disclosure: PepSplain shares an owner with Driftless Research, a peptide retail business, and Daily Peptide Stack, a planned editorial publication. This calculator has no product catalog, affiliate links or sales offers. Shared ownership is disclosed so readers can judge potential conflicts.