mg ↔ mcg
Peptide labels use both milligrams (mg) and micrograms (mcg). They measure the same thing at different scales. Type a number in either box and the other updates instantly.
The larger unit — vial sizes are usually in mg
The smaller unit — doses are usually in mcg
1 milligram always equals 1,000 micrograms.
Quick reference
What's the difference between mg and mcg?
Both measure weight, just at different scales — like feet vs. inches.
- mg (milligram) — one thousandth of a gram. Vial sizes are usually listed in mg (e.g., “5 mg vial”).
- mcg (microgram) — one millionth of a gram, or one thousandth of a milligram. Individual doses are usually listed in mcg (e.g., “250 mcg per injection”).
The rule is simple: 1 mg = 1,000 mcg. To go from mg to mcg, multiply by 1,000. To go from mcg to mg, divide by 1,000.
Why do labels use both?
Vial sizes use mg because the total amount of peptide is large enough that mg keeps the numbers simple (e.g., “5 mg” instead of “5,000 mcg”).
Doses use mcg because individual doses are much smaller, and mcg avoids confusing decimals (e.g., “250 mcg” instead of “0.25 mg”).
This is why it can feel confusing — but once you know the conversion (multiply or divide by 1,000), it becomes second nature.
A real-world example
You have a 5 mg vial of BPC-157 and want to take 250 mcg per dose.
First, convert 250 mcg to mg: 250 ÷ 1,000 = 0.25 mg.
Now you can see how many doses fit in the vial: 5 mg ÷ 0.25 mg = 20 doses.
Our plan builder does all of this math for you automatically — including the syringe units and BAC water amount.