How do you calculate tirzepatide units after reconstitution?

Divide the vial's mg by the bacteriostatic water in mL to get mg/mL. Divide the amount you are working out (in mg) by that concentration to get millilitres, then multiply by 100 for U-100 syringe units. Example: a 30 mg vial in 1.5 mL is 20 mg/mL; 2.5 mg is 0.125 mL, which is 12.5 units. Change the water volume and the unit count changes with it — the concentration is the whole answer.

How much bacteriostatic water do you add to a 30 mg tirzepatide vial?

There is no single right volume, because water sets readability rather than potency. Common choices land the concentration somewhere between 10 and 20 mg/mL: 30 mg in 3 mL is 10 mg/mL, 30 mg in 1.5 mL is 20 mg/mL. Two things constrain the choice — the vial has to physically hold the volume, and the amount you draw should land on a mark you can read. Use the 'Water to add' mode to solve it from either target.

How many units is 2.5 mg of tirzepatide?

There is no universal answer, and any source giving one without stating a concentration is wrong. At 20 mg/mL (a 30 mg vial in 1.5 mL) 2.5 mg is 12.5 units. At 10 mg/mL (the same vial in 3 mL) the same 2.5 mg is 25 units. Units are a volume measurement, not a mass measurement, so the concentration has to come first every time.

Do FDA-approved tirzepatide products need reconstituting?

No — and that is the important distinction. The approved finished products are supplied ready to inject at a fixed concentration and are never mixed by the patient. If you are holding a lyophilized powder and a vial of bacteriostatic water, you are not using an approved product, and neither its contents nor its purity have been verified by anyone. This calculator does not change that; it only converts units.

What happens if I mix up mcg and mg on a tirzepatide vial?

It is a thousand-fold error, and it is the single most common way these calculations go wrong. Tirzepatide amounts are milligram-scale, so a figure written in micrograms is almost always a transcription problem. The calculator flags any amount larger than the whole vial for exactly this reason, but the flag is a backstop, not a check — verify the number against its source.

Is this calculator telling me how much tirzepatide to take?

No. It converts numbers you enter into millilitres and syringe units and does nothing else. Every field starts blank, no amount is suggested, and the vial-strength shortcuts fill a container size rather than a dose. It is not medical advice and not a recommendation to use tirzepatide from any source. Any amount must come from a licensed clinician who knows your history.

Free tool · Tirzepatide vials · Arithmetic only

Tirzepatide Reconstitution Calculator

A lyophilized tirzepatide vial has a mass on the label and nothing else. Before any number on a syringe means anything, that mass and the water you add have to become a concentration in mg/mL — and because tirzepatide is worked out in whole and half milligrams while insulin syringes are marked in hundredths of a millilitre, the conversion is unforgiving.

This runs the same engine as the general peptide calculator, with tirzepatide vial strengths and milligrams already selected. It converts what you type and never proposes an amount.

The math, before you use the tool

Concentration: mg/mL = vial (mg) ÷ bacteriostatic water (mL)
Volume to draw: mL = amount (mg) ÷ concentration (mg/mL)
Syringe units: units = volume (mL) × 100 [U-100: 100 marks = 1 mL]
Draws per vial: draws = vial (mg) ÷ amount (mg)

One unit mark on a U-100 syringe is 0.01 mL. A 30 mg vial in 1.5 mL is 20 mg/mL, so each mark carries 0.2 mg — which is why a single mark misread is a 0.2 mg error at that concentration and a 0.1 mg error at half of it.

Read this before you use the calculator

This tool performs unit arithmetic on numbers you enter, and nothing else. It is not medical advice, it does not recommend a dose, and it is not a suggestion that you use any compound. Most of the peptides these calculators get used with are not FDA-approved for the purposes they are marketed for, are sold through a grey market where purity and labelling are not guaranteed, and many are prohibited in tested sport — check yours with the WADA prohibited-status checker. Any decision to use a compound, and any amount, must come from a licensed clinician who knows your history. The FDA-approved tirzepatide products are supplied ready to inject at a fixed strength and are never reconstituted by the patient — a vial of powder you mix yourself is not one of them, and nothing about its identity, strength or purity has been independently verified.

You already mixed the vial and want to know what a dose looks like on the syringe.

Tirzepatide vial strengths commonly sold

These fill the vial-size field only. A vial strength is what the container holds — it is not a dose, and listing it is not a recommendation to use Tirzepatide.

Peptide in the vialmgThe total peptide mass printed on the vial label.Bacteriostatic water addedmLThe volume you actually drew into the vial.

Dose you are working out

The number you were told to work out — this tool does not propose one. 1 mg = 1000 mcg.

Vial price (optional)USDWhat you paid for the vial. Leave blank to skip cost per dose.

Enter the vial size, the water you added, and the amount you are working out. Every field starts blank on purpose — this tool converts your numbers, it does not supply them.

This is arithmetic, not advice. Every figure above is derived only from the numbers you typed. Nothing here is a recommended dose, a claim that any compound is approved, safe, or effective, or a suggestion that you should use one. Confirm the vial label, the water volume, and the amount with a licensed clinician before you draw anything.

Worked examples

Real numbers, every step shown, so you can check the tool against a pen and paper. These illustrate the arithmetic — the amounts in them are inputs chosen to make the maths legible, not amounts anyone should use.

A 30 mg vial mixed with 1.5 mL, working out 2.5 mg

1Concentration: 30 mg ÷ 1.5 mL = 20 mg/mL
2One unit mark carries 20 ÷ 100 = 0.2 mg
3Volume: 2.5 mg ÷ 20 mg/mL = 0.125 mL
4Units: 0.125 mL × 100 = 12.5 units
5Draws per vial: 30 mg ÷ 2.5 mg = 12

12.5 units — a half-mark, which is the argument for choosing the water differently

The same 30 mg vial mixed with 3 mL instead

1Concentration: 30 mg ÷ 3 mL = 10 mg/mL
2One unit mark carries 0.1 mg
3Volume: 2.5 mg ÷ 10 mg/mL = 0.25 mL
4Units: 0.25 mL × 100 = 25 units
5Draws per vial: unchanged at 12 — water never changes the count

25 units — same vial, same amount, double the water, a mark you can actually read

Solving the water so 2.5 mg lands exactly on 25 units

1water mL = (target units × vial mg) ÷ (amount mg × 100)
2water mL = (25 × 30) ÷ (2.5 × 100)
3water mL = 750 ÷ 250 = 3 mL
4Check the vial holds 3 mL before drawing that much water

3 mL of bacteriostatic water, giving 10 mg/mL

Frequently asked questions

How do you calculate tirzepatide units after reconstitution?: Divide the vial's mg by the bacteriostatic water in mL to get mg/mL. Divide the amount you are working out (in mg) by that concentration to get millilitres, then multiply by 100 for U-100 syringe units. Example: a 30 mg vial in 1.5 mL is 20 mg/mL; 2.5 mg is 0.125 mL, which is 12.5 units. Change the water volume and the unit count changes with it — the concentration is the whole answer.
How much bacteriostatic water do you add to a 30 mg tirzepatide vial?: There is no single right volume, because water sets readability rather than potency. Common choices land the concentration somewhere between 10 and 20 mg/mL: 30 mg in 3 mL is 10 mg/mL, 30 mg in 1.5 mL is 20 mg/mL. Two things constrain the choice — the vial has to physically hold the volume, and the amount you draw should land on a mark you can read. Use the 'Water to add' mode to solve it from either target.
How many units is 2.5 mg of tirzepatide?: There is no universal answer, and any source giving one without stating a concentration is wrong. At 20 mg/mL (a 30 mg vial in 1.5 mL) 2.5 mg is 12.5 units. At 10 mg/mL (the same vial in 3 mL) the same 2.5 mg is 25 units. Units are a volume measurement, not a mass measurement, so the concentration has to come first every time.
Do FDA-approved tirzepatide products need reconstituting?: No — and that is the important distinction. The approved finished products are supplied ready to inject at a fixed concentration and are never mixed by the patient. If you are holding a lyophilized powder and a vial of bacteriostatic water, you are not using an approved product, and neither its contents nor its purity have been verified by anyone. This calculator does not change that; it only converts units.
What happens if I mix up mcg and mg on a tirzepatide vial?: It is a thousand-fold error, and it is the single most common way these calculations go wrong. Tirzepatide amounts are milligram-scale, so a figure written in micrograms is almost always a transcription problem. The calculator flags any amount larger than the whole vial for exactly this reason, but the flag is a backstop, not a check — verify the number against its source.
Is this calculator telling me how much tirzepatide to take?: No. It converts numbers you enter into millilitres and syringe units and does nothing else. Every field starts blank, no amount is suggested, and the vial-strength shortcuts fill a container size rather than a dose. It is not medical advice and not a recommendation to use tirzepatide from any source. Any amount must come from a licensed clinician who knows your history.

The part a calculator cannot answer

A number on a syringe is the easy half. Whether a compound does anything in humans, whether it is legal to buy, and whether it will end a season are the questions worth your time:

Medical disclaimer: This content is for general educational purposes only and is not medical advice, diagnosis, or treatment. Always consult a licensed healthcare professional before starting, stopping, or changing any treatment.

This calculator converts units. It does not account for your health, the specific product in your hand, its actual purity, injection technique, or whether using it is appropriate at all. Nothing on this page states or implies that any compound is FDA-approved, safe, or effective. Talk to a licensed clinician before acting on any figure here.