Reverse Peptide Calculator
A reverse peptide calculator starts with a syringe marking and calculates the amount represented by that volume. Enter the labeled vial mass, the numerical water volume, and the U-100 reading. The tool converts units to mL before applying concentration; it does not choose an amount or decide whether a preparation is appropriate. Here, dose means the calculated mass corresponding to your inputs, not a recommended dose, schedule, route, or treatment. All worked examples are hypothetical arithmetic.
Interactive calculator
The calculator and its inputs load in your browser. The reference below is available without JavaScript.
How to use the peptide calculator
- Read the mass on one vial's label and enter it in mg. A kit's combined mass is not the mass of a single vial.
- Enter the water volume in mL. The calculation assumes this numerical volume when finding mg per mL; it does not prescribe how to prepare the product.
- Enter the syringe reading in U-100 units. These are volume markings, not biological International Units or milligrams.
- Read the volume in mL and the calculated amount in mg and mcg. Check the calibration and all entries, retaining full precision until the displayed result.
The reconstitution formula
Concentration (mg/mL) = labeled vial mass (mg) ÷ entered water volume (mL).
Draw volume (mL) = U-100 syringe units ÷ 100.
Calculated amount (mg) = draw volume (mL) × concentration (mg/mL). Calculated amount (mcg) = mg × 1,000.
Combined formula: amount (mg) = (U-100 units ÷ 100) × (vial mg ÷ water mL).
Worked examples
5 mg in 2 mL, reading of 20 units
Concentration = 5 ÷ 2 = 2.5 mg/mL. A reading of 20 U-100 units represents 20 ÷ 100 = 0.2 mL. Calculated mass = 0.2 × 2.5 = 0.5 mg, or 500 mcg. The example describes an entered volume; it does not recommend that reading.
10 mg in 2 mL, reading of 10 units
Concentration = 10 ÷ 2 = 5 mg/mL. Ten U-100 units represent 0.1 mL. The mass represented is 0.1 × 5 = 0.5 mg, or 500 mcg. The same mass as the preceding example occupies half the volume because the concentration is twice as high.
5 mg in 3 mL, reading of 15 units
Concentration = 5 ÷ 3 mg/mL, a repeating decimal. Fifteen U-100 units represent 0.15 mL. Use full precision: 0.15 × (5 ÷ 3) = 0.25 mg, or 250 mcg. Rounding the concentration early can introduce a small discrepancy.
Same vial mass, twice the water
For a hypothetical 10-unit reading, 5 mg in 1 mL represents 0.5 mg; 5 mg in 2 mL represents 0.25 mg. Doubling the denominator halves concentration and the amount represented by a fixed reading. Conversely, doubling units at a fixed concentration doubles the calculated mass.
Frequently asked questions
What does a reverse peptide calculator calculate?
It converts an entered U-100 syringe reading into mL, then multiplies that volume by labeled vial mass divided by entered water volume. The result is an amount, not an appropriate-dose recommendation.
How many units is 0.1 mL?
On a U-100 syringe, 0.1 mL × 100 = 10 units. These markings describe volume, not milligrams or a substance's biological activity.
How do I convert micrograms to milligrams?
1,000 mcg equals 1 mg. Divide a microgram amount by 1,000: for example, 250 mcg is 0.25 mg. Use matching mass units when dividing by concentration.
Does it work with U-40 or U-50 syringes?
The displayed syringe-unit results use U-100 calibration only. For the same volume, U-40 markings equal mL × 40 and U-50 markings equal mL × 50. A 0.5 mL, 50-unit U-100 syringe is not a U-50 syringe.
Are the examples dosing recommendations?
No. Every example and table entry is hypothetical arithmetic. The calculator converts quantities you supply; it does not determine an appropriate amount, frequency, route, or treatment.
Why do rounded results differ slightly?
Some concentrations repeat indefinitely, such as 5 ÷ 3 mg/mL. Retain full precision during division and round only the final displayed result. The table rounds repeating values for readability.
Does the reverse calculation work for a blend?
A total blend mass gives the combined amount only. To find each component, multiply draw volume by that component's labeled mass divided by shared water volume. Use the blend calculators when individual amounts are needed; the name alone does not determine the ratio.