Dose Volume Calculator
Work out the syringe volume for a specified dose, or calculate the dose from an amount already injected.
What do you want to calculate?
Choose your syringe
Pick the size that matches what your prescriber sent. The diagram below shows the calibration for the size you've chosen.
Vial strength
Most compounded vials are 5 to 10 mg. Read the strength off your pharmacy label.
BAC water added
2 mL is the most common reconstitution volume in Australia. The label tells you exactly how much was added.
Dose
Common starter doses: 250 mcg semaglutide, 2.5 mg tirzepatide. Always match what your prescriber wrote.
Reconstitution guide
Five steps from sealed vial to drawn dose. AU-specific notes throughout.
1. Prepare a clean workspace
Wipe your bench with isopropyl alcohol and let it dry. Have everything in front of you before you open anything: the sealed peptide vial, bacteriostatic water, an alcohol swab, the syringe you sized in step 1, and a sharps container.
Wash your hands and only handle the vial stoppers after wiping each with a fresh alcohol swab. The single biggest cause of cloudy reconstituted vials is touching the rubber stopper before the swab dries.
2. Prepare your materials
Bacteriostatic water in Australia is typically supplied as a 10 mL or 30 mL multi-dose vial. It is preserved with 0.9% benzyl alcohol so it stays sterile across multiple draws when stored properly.
Bring the BAC water to room temperature before reconstitution. Cold water contacting lyophilised peptide is the second most common cause of clouding. If you took it from the fridge, leave it on the bench for 20 minutes.
Compounded peptide vials usually ship with their own BAC water. Only use external BAC water if your pharmacy says you should and they have not provided enough.
3. The art of adding water
Draw the volume of BAC water specified by your pharmacy label (this is the "BAC water added" value you entered above). Insert the needle through the peptide vial's rubber stopper at a slight angle.
Do not squirt water directly onto the lyophilised powder. Tilt the vial and let the water run down the inner glass wall. Withdraw the needle and gently swirl — never shake. Shaking denatures the peptide.
Wait until the powder is fully dissolved (clear, not cloudy) before drawing your first dose. Most peptides dissolve within a minute or two of swirling.
4. A note on concentration
Concentration is purely a function of vial strength divided by water volume. A 5 mg vial reconstituted with 2 mL gives 2.5 mg/mL. The same vial reconstituted with 5 mL gives 1 mg/mL.
Higher concentration means smaller draw volume per dose — better if your dose is small (sub-cutaneous tolerance is roughly 1 mL maximum). Lower concentration means easier dose precision — better if your dose is very small and you want larger syringe markings to read.
If your pharmacy label gives both a strength and a recommended BAC water volume, use those exactly. The calculator above does not invent its own.
5. Storing peptides safely
Unreconstituted (lyophilised) peptide: store in the fridge (2 to 8°C). Long shelf life, generally 12 to 24 months when sealed.
Reconstituted peptide: store in the fridge. Typical stability is 28 days post-reconstitution, but follow the dating your pharmacy provides on the label.
Used syringes: dispose into an Australian-Standard sharps container (yellow lid). Most NSW councils accept sealed sharps at council depots, and some pharmacies offer a take-back service. Never put used syringes in household rubbish — it is a public-health offence in NSW.
Where to inject
Most compounded peptides are given subcutaneously - into the layer of fat just below the skin. These are the four sites with reliable fat coverage for most adults.
- Abdomen - the most common site. Stay at least 5 cm from the navel and rotate between left and right.
- Upper outer thigh - works well if there is enough fat coverage. Lean men may find this site bony.
- Upper outer buttock (gluteal) - reliable fat coverage even on leaner bodies, completely hidden under clothing, and easy to reach across with the opposite hand.
- Back of upper arm - usable but harder to self-inject; often needs help from another person.
Rotate sites every injection. Repeated use of the same spot can cause hardened tissue (lipohypertrophy) that affects absorption. See the site rotation guide for a worked rotation schedule.
Frequently asked questions
How does this calculator work?
It works in two directions. Pick the mode at the top of the page.
Target dose to syringe amount (the default): you tell it the dose you want, it tells you the volume to draw. The arithmetic is: concentration = vial strength ÷ bacteriostatic water volume; volume to draw = dose ÷ concentration. For U-100 syringes, syringe units = volume × 100. Tuberculin syringes are mL-marked, so the answer is shown in mL.
Injected amount to dose: you tell it how much you actually drew (in units or mL), it tells you the dose that was delivered. Same concentration formula, then dose = volume injected × concentration. Useful when you've already drawn or injected and want to confirm what you took.
I drew the wrong amount - what dose did I just take?
Switch to Injected amount to dose at the top. Enter your vial strength, the volume of bacteriostatic water you reconstituted with, and the actual amount you drew (in units if you're on a U-100 syringe, or in mL if you're on a tuberculin syringe). The calculator tells you the delivered dose in mcg or mg.
Don't compensate by skipping or adjusting your next scheduled dose yourself. Ring your prescriber for guidance before injecting again. Note what happened (concentration, volume drawn, calculated dose) so you have it on hand for the call.
My result is a decimal like 5.3 units. Is that OK?
Insulin syringes are marked in whole-unit increments (or half-units on some models). Pull as close to the calculated number as you can and follow your prescriber's instructions on rounding. If your result regularly falls between marks, ask your pharmacy whether a different vial strength or BAC volume would land cleaner.
Which syringe should I use?
For draws under 0.3 mL choose a 0.3 mL U-100 syringe — the markings are larger and easier to read at small volumes. For 0.3 to 0.5 mL choose a 0.5 mL U-100. For larger volumes use a 1 mL U-100. All three are insulin (U-100) syringes, marked in units where 100 units = 1 mL.
What does U-100 mean on the syringe?
U-100 means 100 units per millilitre. It is an insulin-syringe convention. A "20 units" mark on a U-100 syringe is exactly 0.20 mL of liquid — nothing to do with insulin specifically; the mark is just volume in another scale.
Can I use this for tirzepatide or Mounjaro?
The arithmetic works for any reconstituted compounded peptide your prescriber has specified, including compounded tirzepatide. The calculator is unit-agnostic. Branded Mounjaro pens are pre-filled and pre-dosed — the calculator is not relevant to those. Always follow the pharmacy label.
Why does my pharmacy compound differently to the standard?
Australian compounding pharmacies choose vial strength and BAC water volume based on the prescriber's request, the patient's dose, and shelf-life targets. A pharmacy that gives you a 5 mg / 2 mL preparation is not wrong if another pharmacy uses 5 mg / 5 mL — both are valid. Use the values on your specific label.
How do I dispose of used syringes in Australia?
Use an Australian-Standard sharps container (yellow-lidded, AS 4031 or AS 4261). Most local councils run a free sharps disposal program at council depots and selected libraries. Some pharmacies also accept sealed sharps containers. Never place used needles in household rubbish or recycling.
NSW residents can find their nearest disposal point via the EPA's sharps disposal guide.
Further reading
Insulin Syringe Sizes Explained - Which One Do I Need?
Understand 0.5ml vs 1ml U-100 insulin syringes, unit-to-ml markings, 31G 6mm needles and how to choose...
Subcutaneous Injection Technique for Beginners
Step-by-step subcutaneous injection technique for first-timers. Covers site selection, pinch technique, needle angles, anxiety tips and...
How to Dispose of Syringes in Australia
State-by-state guide to safer sharps disposal in Australia. Covers approved sharps containers, pharmacy/council/health-service drop-off options and...
Injection Supplies for Prescribed Compounded Peptides
Guide to sterile syringes, draw needles, alcohol wipes and sharps disposal for label-directed reconstitution workflows under...