Peptide calculator
Reconstitution and dosing maths in one step. Enter what is in the vial and how much water you added, and get the concentration, the volume to draw and the exact mark on the syringe.
What the other calculators leave out
- A single “units” answer that quietly assumes a concentration you never gave it
- Dose figures with nothing behind them — no label, no study, no citation
- Printable dosing charts locked behind an email form
- One syringe scale, as though U-40 barrels did not exist
None of that is hard to fix. It is just work nobody in this niche has bothered to do. Six checks to run against any peptide calculator, including this one.
Calculators by peptide
Each page preloads typical vial sizes and shows the regulatory status and evidence base.
- TirzepatideFDA-approvedDual GIP and GLP-1 receptor agonist approved as Mounjaro (type 2 diabetes) and Zepbound (weight management and obstructive sleep apnea).
- SemaglutideFDA-approvedGLP-1 receptor agonist approved as Ozempic (type 2 diabetes), Wegovy (weight management, cardiovascular risk, MASH) and Rybelsus (oral).
- LiraglutideFDA-approvedOnce-daily GLP-1 receptor agonist approved as Victoza (type 2 diabetes) and Saxenda (weight management).
- RetatrutideNot approved for human useInvestigational triple GIP, GLP-1 and glucagon receptor agonist with positive phase 3 topline results. Not approved anywhere in the world.
- BPC-157Not approved for human useA 15-amino-acid peptide studied almost entirely in rodents. No published human trial supports any of the injury-healing uses it is sold for, and no dose per kilogram of body weight exists for people.
- TB-500Not approved for human useA name that covers two different molecules. Real human trials exist for one of them — none used the injectable musculoskeletal route TB-500 is actually sold for.
- CJC-1295Not approved for human useSynthetic 29-amino-acid GHRH analogue. One published human study from 2006; the FDA's advisory committee voted against it in 2024 for lack of effectiveness evidence.
- IpamorelinNot approved for human useSelective growth hormone secretagogue with exactly one published human study — a single-dose intravenous pharmacokinetic trial from 1999.
- MOTS-cNot approved for human useA 16-amino-acid mitochondrial-derived peptide. Every efficacy dose ever published for MOTS-c itself was given to a mouse by intraperitoneal injection; no human dose has been published.
How the maths actually works
Reconstitution is one division followed by one multiplication. The peptide arrives as a freeze-dried powder of a known mass. You add a known volume of liquid. Dividing the first by the second gives you a concentration, and every other number falls out of it.
A worked example: a 10 mg vial with 2 mL of bacteriostatic water gives 5 mg/mL. A 2 mg dose is therefore 2 ÷ 5 = 0.4 mL, and 0.4 mL on a U-100 syringe is 40 units. The same vial with 1 mL of water would be 10 mg/mL, and that same 2 mg dose would be 20 units instead. The dose did not change. Only the number you read off the barrel did.
Why “how many units is 2.5 mg” has no answer
This is the most-searched question in peptide dosing and most pages answer it with a number, which is not possible. Milligrams measure mass. Units on an insulin syringe measure volume — one unit is one hundredth of a millilitre. Converting between them requires knowing how concentrated your solution is, and that is something you chose when you decided how much water to add.
Two people can both hold a 2.5 mg dose and correctly draw completely different amounts. If one added 2 mL to a 10 mg vial and the other added 4 mL, the first draws 5 units and the second draws 10. Both are right. Anyone quoting a single conversion is quietly assuming a concentration they have no way of knowing. The converter works it out from your own vial.
Choosing how much water to add
Since the water only sets concentration, choose it to make your dose comfortable to measure. A draw below about 5 units is hard to read accurately, and small errors there become large percentage errors in the dose. A draw above the barrel’s capacity means splitting into two injections. Somewhere between 10 and 50 units is the practical sweet spot, and the calculator flags you when you fall outside it.
There is a second constraint people forget: the vial itself. Most peptide vials hold about 3 mL, so you physically cannot add 5 mL of water no matter what the arithmetic says.
U-100, U-40 and a 2.5× error
Every insulin syringe sold for human use is U-100: one hundred units per millilitre. That is why a 0.3 mL, 0.5 mL and 1 mL barrel all give the same unit reading for the same dose — they differ in capacity and in how finely they are printed, not in scale.
U-40 syringes are a different scale, sold for veterinary insulin, and they are easy to end up with by accident. Forty units per millilitre means the same volume reads a different number: 0.4 mL is 40 units on a U-100 barrel and 16 units on a U-40 one. Using a U-40 syringe with a chart written for U-100 gives a 2.5-fold dosing error. Most calculators do not even offer the choice; this one does, and redraws the syringe to match.
Where our numbers come from
The arithmetic above is just arithmetic — it is the same for any substance in any vial. The dosing information on our individual peptide pages is a different matter, and it is where most sites in this niche quietly make things up.
We split every compound into one of two tracks. Drugs with an FDA label get their titration schedules reproduced from that label, cited to it. Compounds without approval anywhere get no dosing schedule at all — instead we list the doses that appeared in named published studies, tagged with the species and route, because a dose given to a rat is not a human dose. Where nothing reliable has been published, the page says so rather than filling the gap. Read the full methodology.
Common questions
Sources used on this page
Every number on this page comes from one of the documents below. Where no reliable source exists, the page says so instead of filling the gap.
- FDA labelFDA / DailyMed· 2026-08MOUNJARO (tirzepatide) injection — FDA prescribing information
- FDA labelFDA / DailyMed· 2026-08ZEPBOUND (tirzepatide) injection — FDA prescribing information
- FDA labelFDA / DailyMed· 2026-05OZEMPIC (semaglutide) injection — FDA prescribing information
- FDA labelFDA· 2026-03WEGOVY (semaglutide) injection and tablets — FDA prescribing information
- RegulatorFDA· 2026-05-14Bulk Drug Substances Nominated for Use in Compounding Under Section 503A
- RegulatorFDA· 2026-09-01FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss