Peptide Dosage Reference: Units, mcg, mg

How many units is 100 mcg or 250 mcg?

It depends on the concentration: units = amount in mcg ÷ concentration in mcg/mL × 100. With 5 mg in 2 mL (2.5 mg/mL, or 2,500 mcg/mL), 100 mcg is 4 units and 250 mcg is 10 units; read the other way, 10 units holds 250 mcg. 1 mg = 1,000 mcg, and on a U-100 syringe 100 units = 1 mL.

Reconstitution calculator

Type your own numbers. They aren't sent anywhere: the math runs in your browser.

Peptide in the vial (mg) Water added (mL)

Amount per draw

mcg mg

Concentration

2.5 mg/mL

Volume to draw

—

U-100 units

—

Type an amount to see the volume and the units.

Arithmetic only. Peptly does not suggest amounts: the amount is yours, from your protocol or the product's documentation. Not medical advice.

Unit reference

• mcg (microgram) — 1/1,000 of a mg. Common for small-dose research peptides (e.g. BPC-157 at 250 mcg).
• mg (milligram) — common for GLP-1 / GIP-GLP-1 peptide dosing (e.g. semaglutide at 0.25 mg).
• ml (milliliter) — volume drawn into the syringe.
• mg/ml (concentration) — how much peptide mass is in each ml of reconstituted solution.
• U-100 unit — 0.01 ml. 100 units fills a 1 ml U-100 syringe.
• U-40 unit — 0.025 ml. 40 units fills a 1 ml U-40 syringe.

Conversion formulas

1. mcg → mg: divide by 1,000.
2. mg → mcg: multiply by 1,000.
3. Concentration: vial mass (mg) ÷ BAC water (ml) = mg/ml.
4. Draw volume: target dose (mg) ÷ concentration (mg/ml) = ml.
5. U-100 units: ml × 100.
6. U-40 units: ml × 40.

Common error patterns

• mg / mcg mix-up. A 250 mg dose is 1,000× a 250 mcg dose. Always verify units.
• U-100 / U-40 mix-up. 10 units on U-100 (0.1 ml) is far less than 10 units on U-40 (0.25 ml).
• Stale concentration. If a new vial gets a different BAC water volume, the old concentration no longer applies — work it out again.
• Inconsistent decimal handling. 0.25 mg is the same as 250 mcg — write the unit every time to avoid confusion.

See also

• Main peptide calculator
• Reconstitution math reference
• BAC water calculator
• How to reconstitute peptides

Frequently asked questions

What is the difference between mcg and mg? +

1 mg = 1,000 mcg. mcg is microgram, mg is milligram. The factor of 1,000 between them is the most common source of error in reconstitution math — the calculator on this page always shows the unit explicitly to avoid ambiguity.

How do I convert mg/ml to U-100 units? +

U-100 units = draw volume (ml) × 100. To get the draw volume, divide the target dose (mass) by the concentration (mg/ml). Example: 250 mcg at 2.5 mg/ml = 0.1 ml = 10 units on U-100.

What is a U-100 syringe? +

A U-100 insulin syringe is scaled so that 100 units = 1 ml. Each unit mark represents 0.01 ml. This is the most common reference scale in research peptide use.

What is the difference between U-100 and U-40? +

U-100 has 100 units per ml (1 unit = 0.01 ml). U-40 has 40 units per ml (1 unit = 0.025 ml). The same number of units on different scales is a different volume. The calculator on this page uses U-100.

Does Peptly recommend dosing? +

No. The calculator on this site does arithmetic on the numbers you enter, and the Peptly app is a log that keeps what you type; neither suggests an amount. Values shown are arithmetic outputs — not medical advice, not dosing recommendations. Consult a licensed clinician before any injection.