How the math works
Every number on this site comes from the formulas below. There are no lookup tables of amounts, no substance-specific factors and nothing hidden.
1. Concentration
C (mcg/mL) = C (mg/mL) × 1,000
M is the mass printed on the vial label and reported on the lot certificate. V is the solvent you add. The powder's own volume is ignored (see the questions below). Example: 5 mg ÷ 2 mL = 2.5 mg/mL = 2,500 mcg/mL.
2. Draw volume
A and C must share the mass unit. The calculators convert everything to micrograms internally. Example: 250 mcg ÷ 2,500 mcg/mL = 0.1 mL.
3. Syringe units
S = 100 for a U-100 syringe, 40 for a U-40 syringe
S is the scale printed on the barrel. Barrel size (0.3, 0.5, 1 mL) does not change S; it only sets the maximum readable units (30, 50, 100 on U-100). Example: 0.1 mL × 100 = 10 units.
4. Mass per unit
The most useful single number once a vial is made up. At 2,500 mcg/mL on U-100 each unit carries 25 mcg.
5. Draws per vial
Rounded down to whole draws. V does not appear: the solvent volume cannot change how much mass the vial holds. Example: 5,000 ÷ 250 = 20.
6. Cost
per mg = per vial ÷ M (mg)
per draw = per mg × A (mg per draw)
7. Water to add (working backwards)
from a target unit count: C = A ÷ (units ÷ S), then V = M ÷ C
8. Blends
v = A_A ÷ C_A · B carried = v × C_B
Two masses in one solvent volume give two concentrations. A draw sized for A carries B at the label ratio M_A : M_B.
9. Conversions
| 1 mg | = 1,000 mcg (µg) |
| 1 mL | = 1 cc = 1,000 µL |
| 1 mg/mL | = 1,000 mcg/mL |
| 1 U-100 unit | = 0.01 mL = 10 µL |
| 1 U-40 unit | = 0.025 mL = 25 µL |
| IU | activity unit, no universal mass equivalent |
Rounding
Calculations are carried at full precision and rounded only for display: concentration to 3 decimals, millilitres to 2 decimals (3 below 0.1 mL, 4 below 0.01 mL), units to 1 decimal (2 below 1 unit), money to cents. Draws per vial are always rounded down. The static tables on the vial pages use the same functions as the live calculators, so the two never disagree.
Dose ranges
The dosage charts are not calculated; they are collected. Each range states its basis (FDA label, published trial, or commonly reported) and links the source. The units column on a chart is formulas 1 to 3 applied to that range at the stated mix.
Questions
Are the calculators exact?
The arithmetic is exact. Displayed values are rounded: millilitres to 2 decimals (3 or 4 below 0.1 mL), units to 1 decimal, concentration to 3 decimals. Rounding happens at display time, never between steps.
Why does the calculator treat the final volume as the water volume?
A few milligrams of lyophilized powder add a negligible volume to a millilitre or more of solvent. For very large masses in very small volumes the true concentration is slightly lower than mass ÷ solvent; that case is outside what these tools are built for.
Does the site store my inputs?
No. Every calculation runs in your browser. The share link encodes the inputs in the URL so you can bookmark it; nothing is sent to a server.