Peptide Calculator —
Reconstitution & Dosage

A peptide reconstitution calculator is a tool that helps you determine the exact volume to draw in your syringe for a specific peptide dose. You input the peptide vial size (in mg), the amount of bacteriostatic water you added (in ml), and your desired dose (in mcg), and the calculator tells you how many units to draw on your insulin syringe.

Reconstituting peptides means adding bacteriostatic water to a lyophilized (freeze-dried) peptide vial to create an injectable solution. Use sterile technique: swab the tops of both vials, inject the bacteriostatic water slowly against the glass wall, then gently swirl until fully dissolved. After reconstitution, refrigerate the vial and follow your clinician or pharmacy instructions.

To mix (reconstitute) peptides, draw the recommended volume of bacteriostatic water (BAC water) into a sterile syringe, inject it slowly into the peptide vial (aiming the stream at the glass wall), and gently swirl until the solution becomes clear. Do not shake vigorously. The amount of BAC water you add determines your concentration (mg/mL) and how many insulin syringe units you draw per dose.

To calculate your peptide dose, use this three-step formula: (1) Divide the vial quantity in mg by the water volume in ml to get the concentration in mg/ml. (2) Divide your desired dose in mcg by the concentration × 1,000 to get the injection volume in ml. (3) Multiply the injection volume by the total syringe units divided by the syringe volume to convert to syringe units. For example, a 5mg vial reconstituted with 2ml of bacteriostatic water gives a 2.5 mg/ml concentration. A 250 mcg dose requires 0.1 ml, which equals 10 units on a 100-unit (1 ml) syringe.

The most common reconstitution volumes for a 5mg peptide vial are 1 ml or 2 ml of bacteriostatic water. Using 1 ml creates a 5 mg/ml concentration (more concentrated, smaller injection volume), while 2 ml creates a 2.5 mg/ml concentration (easier to measure smaller doses). Not sure how much water to add? Use our BAC water calculator to get a recommended amount based on your vial size and dose. Your prescribing clinician will also recommend the appropriate volume based on your specific peptide and dosing protocol.

Milligrams (mg) and micrograms (mcg) are both units of weight. 1 mg equals 1,000 mcg. Peptide vials are typically labeled in milligrams (e.g., 5 mg, 10 mg), while individual doses are usually measured in micrograms (e.g., 250 mcg, 500 mcg). This is because each dose is a small fraction of the total vial contents.

Units on an insulin syringe refer to volume markings. A 100-unit syringe holds 1 ml total, so each unit equals 0.01 ml. A 50-unit syringe holds 0.5 ml (each unit = 0.01 ml), and a 30-unit syringe holds 0.3 ml (each unit = 0.01 ml). The "units" are not related to drug potency — they are simply volume markers that make it easier to measure small injection volumes accurately.

The number of doses per vial depends on the vial size and your dose amount. Divide the total vial quantity (in mcg) by your dose (in mcg). For example, a 5 mg vial (5,000 mcg) at 250 mcg per dose yields 20 doses. A 10 mg vial at 500 mcg per dose also yields 20 doses. Our calculator automatically shows your doses-per-vial count.

Sterile water for injection (SWFI) can be used but is not ideal for multi-dose vials. Bacteriostatic water contains 0.9% benzyl alcohol as a preservative, which inhibits bacterial growth and allows safe use over multiple injections for up to 28 days. Sterile water has no preservative, so it should only be used for single-dose applications. Always follow your healthcare provider's instructions.

Reconstituted peptides typically remain stable for 3-4 weeks when stored at 2-8°C (36-46°F) in a standard refrigerator. For longer storage, peptide solutions can be frozen at -20°C for 3-4 months. Avoid repeated freeze-thaw cycles. Unreconstituted lyophilized powder is far more stable and can be stored at -20°C for years.

Most peptide users use insulin syringes, which come in three common sizes: 0.3 ml (30 units), 0.5 ml (50 units), and 1.0 ml (100 units). For small doses, a 0.3 ml syringe provides the finest graduation marks and greatest accuracy. For larger doses, a 0.5 ml or 1.0 ml syringe may be necessary to hold the full injection volume. Use the smallest syringe that can accommodate your dose for the most accurate measurement.

Yes, our peptide reconstitution calculator is completely free to use with no signup or registration required. It works on all devices — desktop, tablet, and mobile. You can use it as many times as needed to calculate dosing for any injectable peptide.

To reconstitute compounded semaglutide, add bacteriostatic water to the lyophilized vial using sterile technique. A common setup is 2 ml of bacteriostatic water into a 5 mg vial, yielding a 2.5 mg/ml concentration. Inject the water slowly against the glass wall at a 45° angle, then gently swirl until dissolved. Starting dose is typically 0.25 mg (250 mcg) per week, which is 0.1 ml or 10 units on a 100-unit syringe at this concentration. Always follow your prescribing provider's specific instructions.

Most peptide injections use a 29-gauge or 31-gauge insulin syringe with a ½-inch needle for subcutaneous injection. Thinner gauges (higher numbers) cause less discomfort. For subcutaneous injections, a ½-inch needle is sufficient for most body composition types. Common injection sites include the lower abdomen, thigh, or upper arm. Your healthcare provider will recommend the appropriate needle gauge and injection site for your protocol.

The number of insulin syringe units for a BPC-157 dose depends on how you reconstitute it. For a common setup of 5 mg BPC-157 reconstituted with 2 ml bacteriostatic water (2.5 mg/ml concentration), a 250 mcg dose equals 10 units on a 100-unit syringe, and a 500 mcg dose equals 20 units. Use our peptide calculator above to determine the exact units for your specific reconstitution setup.

Some peptides can be drawn into the same syringe for a single injection, but they should generally not be reconstituted in the same vial. Peptides like CJC-1295 and Ipamorelin are commonly combined in one syringe since they are designed to work synergistically. However, mixing incompatible peptides can cause degradation or reduced efficacy. Always consult your healthcare provider before combining peptides, and never mix peptides that have different storage requirements or pH sensitivities.

For a 10 mg vial, the calculation follows the same formula. If you add 2 ml of bacteriostatic water, the concentration is 10 mg ÷ 2 ml = 5 mg/ml (5,000 mcg/ml). For a 250 mcg dose: 250 mcg ÷ 5,000 mcg/ml = 0.05 ml = 5 units on a 100-unit syringe. For a 500 mcg dose: 500 mcg ÷ 5,000 mcg/ml = 0.1 ml = 10 units. A 10 mg vial at 250 mcg per dose provides 40 doses total.