Research Use Only. Every compound referenced on this page is supplied for laboratory and analytical research. Nothing here is for human or veterinary use, ingestion, injection, or any form of administration. The tables on this page are preparation arithmetic for laboratory protocol reference: they convert a labelled peptide mass and a diluent volume into a solution concentration. They are not a dosing chart, they do not describe an administration schedule, and no figure on this page should be read as a recommended amount of anything for a person or an animal.
Quick Answer: The Reconstitution Formula
Concentration equals total peptide mass divided by diluent volume. A 10mg vial reconstituted with 2mL of bacteriostatic water yields 5 mg/mL, or 5,000 mcg/mL. The arithmetic never changes with the compound: only the two input numbers do. Multiply any mg/mL figure by 1,000 to express it in mcg/mL.
The Master Peptide Reconstitution Chart
Ten vial masses crossed against the five bacteriostatic water volumes that come up most often, with each result given in both mg/mL and mcg/mL.
Vial mass | 1 mL | 2 mL | 3 mL | 5 mL | 10 mL |
|---|---|---|---|---|---|
2 mg | 2 mg/mL | 1 mg/mL | 0.67 mg/mL | 0.4 mg/mL | 0.2 mg/mL |
5 mg | 5 mg/mL | 2.5 mg/mL | 1.67 mg/mL | 1 mg/mL | 0.5 mg/mL |
10 mg | 10 mg/mL | 5 mg/mL | 3.33 mg/mL | 2 mg/mL | 1 mg/mL |
15 mg | 15 mg/mL | 7.5 mg/mL | 5 mg/mL | 3 mg/mL | 1.5 mg/mL |
20 mg | 20 mg/mL | 10 mg/mL | 6.67 mg/mL | 4 mg/mL | 2 mg/mL |
30 mg | 30 mg/mL | 15 mg/mL | 10 mg/mL | 6 mg/mL | 3 mg/mL |
50 mg | 50 mg/mL | 25 mg/mL | 16.67 mg/mL | 10 mg/mL | 5 mg/mL |
70 mg | 70 mg/mL | 35 mg/mL | 23.33 mg/mL | 14 mg/mL | 7 mg/mL |
80 mg | 80 mg/mL | 40 mg/mL | 26.67 mg/mL | 16 mg/mL | 8 mg/mL |
100 mg | 100 mg/mL | 50 mg/mL | 33.33 mg/mL | 20 mg/mL | 10 mg/mL |
Two columns in that grid carry most of the real-world traffic. The 2mL and 3mL columns are what researchers reach for the overwhelming majority of the time, because they land common vial masses on concentrations that are convenient to measure without being so dilute that the working solution outlives its usable window. The 1mL column exists mainly for small vials, or for anyone deliberately making a concentrate to dilute further downstream.
The 5mL and 10mL columns come with a physical constraint that no table can show you. A great many research vials are 3mL vials, including every lyophilized presentation in the 99 Purity Peptides catalogue referenced further down this page. You cannot put 5mL of diluent into a 3mL vial. Those two columns are here because larger-format vials exist and because researchers building serial dilutions ask for them, not because they are options for a standard 3mL cap-and-crimp vial. Check the vial before you check the chart.
How the Formula Works, and How to Verify a Number by Hand
The whole thing is one division. Concentration (mg/mL) = peptide mass (mg) ÷ diluent volume (mL). Mass on top, volume on the bottom.
The reason it holds is that lyophilized peptide occupies almost no volume once dissolved. When you add 2mL of bacteriostatic water to a vial of freeze-dried powder, the final solution volume is, for practical purposes, still 2mL. The mass of powder in a 10mg vial is ten thousandths of a gram sitting as a thin cake at the bottom of the glass, and its contribution to final volume falls far below what you could resolve on a syringe barrel. That is why the calculation treats diluent volume and solution volume as the same number, and why nobody bothers with a displacement correction the way you would for a concentrated suspension.
Worked example one. A 30mg vial, 3mL of bacteriostatic water. 30 ÷ 3 = 10. The solution is 10 mg/mL. Converted to micrograms, that is 10,000 mcg/mL, and every 0.1mL drawn from that vial contains 1mg of labelled peptide mass.
Worked example two, run backwards. Suppose the target is 5 mg/mL and the vial is 20mg. Rearranged, volume = mass ÷ concentration, so 20 ÷ 5 = 4mL. That reverse form is the more useful one in practice, because researchers usually know the concentration they want and need the volume that produces it, rather than the other way round.
Unit conversion trips people more often than the division does. A milligram is 1,000 micrograms, so 2.5 mg/mL and 2,500 mcg/mL describe the same solution two ways. Nothing has been diluted or concentrated between those two numbers. Vendors and calculators switch between the units without warning, which is why both appear in every cell of the chart above.
Note: The formula gives you the concentration of labelled peptide mass per millilitre. It does not account for net peptide content, which is a separate correction covered later on this page. For a full narrative walkthrough of reconstitution technique rather than the arithmetic, see the peptide calculator reconstitution guide and how much bacteriostatic water to use when reconstituting peptides.
Per-Compound Quick Reference
Vial masses vary by compound, and the chart above only helps once you know which row you are actually in. These are lyophilized presentations currently listed in the 99 Purity Peptides catalogue, with the resulting concentration at the two volumes a 3mL vial can physically accommodate.
Compound | Vial mass(es) | At 2 mL | At 3 mL | Full reference |
|---|---|---|---|---|
80 mg total (4-component blend) | 40 mg/mL total | 26.67 mg/mL total | ||
70 mg total (3-component blend) | 35 mg/mL total | 23.33 mg/mL total | ||
5 mg / 10 mg | 2.5 / 5 mg/mL | 1.67 / 3.33 mg/mL | ||
5 mg / 10 mg | 2.5 / 5 mg/mL | 1.67 / 3.33 mg/mL | ||
5mg+5mg (10 mg total) / 10mg+10mg (20 mg total) | 5 / 10 mg/mL total | 3.33 / 6.67 mg/mL total |
Notice what separates the top two rows from the middle two. A single-compound vial gives a concentration that means exactly one thing. KLOW, GLOW, and the BPC-157/TB-500 blend give a total concentration, and total is not the number most protocols need. That distinction gets its own section below, because it is the most consequential error in this whole topic.
Vial strengths change. Before committing a number to a protocol, confirm the mass printed on the vial you physically hold against the product page and the lot certificate, not against a chart written at some earlier date.
Bacteriostatic Water to Syringe Unit Conversions
A U-100 insulin syringe is graduated so that 100 units fills exactly 1mL. The unit markings on the barrel are volume graduations and nothing more: a fine-resolution ruler for small volumes, where each unit marking on a U-100 barrel equals 0.01mL.
Volume | U-100 barrel | U-40 barrel |
|---|---|---|
0.05 mL | 5 units | 2 units |
0.1 mL | 10 units | 4 units |
0.2 mL | 20 units | 8 units |
0.25 mL | 25 units | 10 units |
0.5 mL | 50 units | 20 units |
1.0 mL | 100 units | 40 units |
The second column is where measurement errors originate. U-40 barrels are calibrated at 40 units per millilitre rather than 100, so the same physical volume reads as a completely different number of units depending on which barrel you picked up. Merck Animal Health documents the size of that gap in the veterinary insulin context: reading a U-40 preparation on a U-100 barrel delivers under half the intended volume, and the reverse mistake delivers roughly two and a half times it (Merck Animal Health, Vetsulin syringe administration guidance). The factor is 2.5 in either direction. Nothing about the peptide changed; the ruler changed.
U-40 barrels are uncommon outside veterinary supply chains, which is exactly why they cause trouble when one turns up in a mixed box of consumables. Read the barrel print before the first draw from a new pack.
For the complete volume-to-unit reference across the full range, including the intermediate volumes omitted here, use the dedicated bacteriostatic water to insulin syringe unit conversion chart.
Does Net Peptide Content Change These Numbers?
It changes what the number means, not what you calculate.
Lyophilized peptide powder is not pure peptide by weight. It also carries counterions and residual water. Solid-phase synthesis uses trifluoroacetic acid for cleavage and again as an ion-pairing reagent during purification, so synthetic peptides are typically isolated as trifluoroacetate salts, with TFA bound to basic residues and the free N-terminus (Erckes et al., Pharmaceuticals, 2025). Peptides are also hygroscopic to a sequence-dependent degree, so some non-covalently bound water persists even after freeze-drying.
The label mass is therefore gross weight. Net peptide content, the fraction of that gross weight which is actually peptide, commonly falls around 60–80% for synthetic peptides, measured by quantitative amino acid analysis or elemental analysis (Biosynth, peptide analytics documentation).
Net content can also be estimated from structure before any assay is run. Divide the peptide's molecular weight by that weight plus the number of counterion binding sites multiplied by the counterion's molecular weight (114 for trifluoroacetate, 59 for acetate). A peptide of MW 1,000 with two available TFA binding sites works out to 1,000 ÷ (1,000 + 228), or roughly 81% (AmbioPharm technical FAQ). More basic residues in the sequence means more counterion in the powder and a lower net content.
Here is what that does to a familiar row of the master chart. A 10mg vial in 2mL is 5 mg/mL of labelled mass in every case; only the peptide actually delivered moves.
Net peptide content | Actual peptide in vial | Actual concentration at 2 mL |
|---|---|---|
100% (theoretical) | 10 mg | 5 mg/mL (5,000 mcg/mL) |
85% | 8.5 mg | 4.25 mg/mL (4,250 mcg/mL) |
80% | 8 mg | 4 mg/mL (4,000 mcg/mL) |
75% | 7.5 mg | 3.75 mg/mL (3,750 mcg/mL) |
70% | 7 mg | 3.5 mg/mL (3,500 mcg/mL) |
At 75% net content, a protocol written against the label figure is running a quarter below the concentration it believes it has. For qualitative work that margin is often tolerable. For anything quantitative, anything compared across lots, or anything another lab will try to replicate, it is not, and it is a common silent source of between-batch disagreement. The correction uses the same division as before, applied to the corrected mass: net peptide mass ÷ diluent volume.
Net peptide content and HPLC purity answer different questions, and conflating them is its own error. Purity describes what proportion of the peptide present is the target sequence rather than deletion sequences or synthesis byproducts. Net content describes what proportion of the powder is peptide at all. A vial can be 99% pure and 72% net peptide at the same time, with both figures correct.
Multi-Component Blends: Why One Table Isn't Enough
A blend's total concentration is not any single component's concentration. This is where the master chart stops being sufficient.
Take the KLOW vial. It holds 80mg of total peptide mass, distributed as one component at 50mg and three at 10mg each. Reconstitute with 2mL and the master chart gives 40 mg/mL, which is correct and close to useless on its own, because nothing in that vial exists at 40 mg/mL. The 50mg component sits at 25 mg/mL. Each 10mg component sits at 5 mg/mL. All four were co-lyophilized, which locks them in a fixed ratio: every aliquot drawn afterwards carries all four at that ratio, and no choice of diluent volume can separate them.
The same reasoning applies to the 70mg GLOW vial, and to the BPC-157/TB-500 blend, where the 10mg+10mg presentation produces 10 mg/mL total at 2mL but 5 mg/mL of each component.
The practical rule: divide each component's individual mass by the diluent volume, never the total. The KLOW reconstitution and storage reference works this problem in full, component by component, and is the better page to keep beside the bench for blend work.
Common Reconstitution Mistakes
Six errors account for most concentration disagreements that surface after the fact.
Treating total blend concentration as per-component concentration. Covered above, and comfortably the most expensive item on this list, because it produces a number that is arithmetically correct and experimentally wrong.
Misreading the vial's fill volume as an instructed diluent volume. The KLOW product listing reads "KLOW 50mg/10mg/10mg/10mg 3ML". That 3ML is the capacity of the glass, the same way any other 3mL vial is described. It is not an instruction to add 3mL. Vendors across this category label vials this way, and researchers new to the format routinely read a container specification as a protocol step. Diluent volume is your decision, constrained only by headspace.
Using sterile water instead of bacteriostatic water for a multi-draw vial. Bacteriostatic Water for Injection USP contains 0.9% (9 mg/mL) benzyl alcohol as a bacteriostatic preservative and is supplied in multiple-dose containers precisely so repeated withdrawals can be made (Hospira, DailyMed label). Sterile Water for Injection USP contains no bacteriostat, no antimicrobial agent, and no added buffer, and its label states it is supplied only in single-dose containers with the unused portion discarded (DailyMed, Sterile Water for Injection USP). The wrong choice does not change the concentration at all. It changes how many times the vial can be entered.
Shaking instead of swirling. Agitation is a well-characterized aggregation trigger, and the mechanism is the air–liquid interface rather than the motion itself. Work reviewed in The AAPS Journal found that agitating a protein in a vial with air headspace produced extensive aggregation, while shaking under otherwise identical conditions without headspace substantially limited it (Li et al., AAPS J, 2019). A partly filled research vial is mostly headspace. Direct the diluent down the inner wall rather than onto the cake, then swirl.
Skipping the net peptide content correction. A quiet 20–30% offset that will not announce itself until someone tries to reproduce the work.
Repeated freeze-thaw of a working vial. Cysteine, methionine, and tryptophan residues are oxidation-prone, and freeze-thaw cycling accelerates that oxidation (Rehman et al., Advanced Drug Delivery Reviews, 2023). Aliquot once into single-use volumes rather than cycling one vial through the freezer repeatedly.
Storage and Handling Quick Reference
Condition | Storage | Practical horizon |
|---|---|---|
Lyophilized, sealed, in transit | Ambient, brief | Days |
Lyophilized, long-term | −20 °C, protected from light, dry | Several years for most sequences |
Reconstituted, in active use | 2–8 °C | Short-term working use |
Reconstituted, frozen aliquots | −20 °C | Weeks |
Reconstituted, extended storage | −80 °C | Months |
Lyophilized material is the stable form by a wide margin. Removing water removes the medium in which hydrolysis and deamidation proceed, which is why the same sequence that survives years as a dry cake at −20 °C protected from light degrades on a far shorter clock once it is in solution (Rehman et al., Advanced Drug Delivery Reviews, 2023).
Two degradation routes matter most once a vial is wet. Deamidation is base-catalyzed and runs fastest where an asparagine or glutamine sits next to a glycine, proceeding through a cyclic imide intermediate to aspartate and iso-aspartate products. Oxidation targets cysteine and methionine, and cysteine oxidation accelerates at higher pH as the thiol deprotonates and forms disulfide bonds (Sigma-Aldrich, peptide stability technical documentation). Prolonged exposure above pH 8 is worth avoiding for both reasons, and bacteriostatic water sits comfortably below that at pH 5.7 (Hospira, DailyMed label).
Treat the horizons above as general patterns rather than a specification for any particular sequence. Sequence composition is the primary determinant of stability, so a lot certificate for the material in hand overrides any general table, this one included.
Verifying the Numbers on Your Own Vial
No generic chart knows your lot. A certificate of analysis does.
Three fields change what the master chart means for the vial in front of you. Stated peptide mass confirms which row you are actually in. Net peptide content, where reported, gives a real correction factor instead of an assumed 60–80% band. HPLC purity tells you what fraction of the peptide is the target sequence, which remains a separate question from how much peptide is in the powder.
Certificates are lot-specific. The COA linked from a product page corresponds to one particular batch, and the next batch gets its own document with its own numbers. Match the lot code on the certificate to the lot code on the vial before trusting either. For a field-by-field walkthrough of what each section of the document is telling you, see how to read a certificate of analysis, and browse current lot documentation at certificates.
Working From the Chart
This page exists to hand you the numbers without making you compute them, and to give search engines and answer engines those same numbers in plain HTML rather than behind a script. For anything the grid above does not cover, including target-concentration work and volumes falling between the columns shown, the peptide calculator and the peptide reconstitution calculator accept arbitrary inputs. Current batch documentation lives at certificates. Verify the vial, verify the lot, then do the division.
Frequently Asked Questions
How much bacteriostatic water should I use for a 10mg vial?
Whatever volume produces the concentration your protocol calls for. 1mL gives 10 mg/mL, 2mL gives 5 mg/mL, and 3mL gives 3.33 mg/mL. There is no single correct answer, because the volume is an input you choose rather than a property of the vial. Most 10mg work lands on 2mL simply because it produces round arithmetic.
What concentration does a 5mg vial in 2mL give?
2.5 mg/mL, which is the same solution as 2,500 mcg/mL. Every 0.1mL drawn contains 0.25mg of labelled peptide mass. If the lot certificate reports net peptide content below 100%, multiply 2.5 by that fraction to get the actual peptide concentration.
How many units on a U-100 syringe is 0.25mL?
25 units. A U-100 barrel is graduated so 100 units equals 1mL, making each unit marking 0.01mL. On a U-40 barrel the same 0.25mL reads as 10 units instead, because that barrel is calibrated at 40 units per millilitre.
Does "3ML" on a vial label mean I should add 3mL of water?
No. That figure describes the capacity of the glass vial, not a diluent instruction. A 3mL vial can accept 1mL, 2mL, or close to 3mL depending on the concentration you want. The mass figure on the label is the specification that matters for the calculation.
Can I use sterile water instead of bacteriostatic water?
Sterile Water for Injection USP contains no preservative, and its label specifies single-dose containers with the remainder discarded. Bacteriostatic water contains 0.9% benzyl alcohol and is supplied for repeated withdrawals. Neither choice changes the concentration arithmetic. The difference is entirely about how many times the vial can be entered.
Why doesn't this chart match the number my calculator gave me?
Check three things in order: whether one figure is in mg/mL and the other in mcg/mL, whether you entered total blend mass where the calculator expected a single component, and whether one of the two applied a net peptide content correction. Those three account for nearly every mismatch.
What is the concentration of an 80mg KLOW vial reconstituted with 2mL?
40 mg/mL of total peptide mass. That total is not any individual component's concentration. The 50mg component sits at 25 mg/mL and each 10mg component at 5 mg/mL. Blend protocols almost always need the per-component figures rather than the total.
Is 10 mg/mL the same thing as 10,000 mcg/mL?
Yes, identical solutions. One milligram contains 1,000 micrograms, so converting between the units is a multiplication or division by 1,000 with no change to the solution itself. Suppliers and calculators switch between them freely, which is why both appear throughout this page.
Does net peptide content change how much water I should add?
Not the volume, only the interpretation. You still add the volume that gives your target labelled concentration. What changes is the peptide actually delivered: at 75% net content, a nominal 5 mg/mL solution contains 3.75 mg/mL of peptide. Apply the correction to the mass, then divide as normal.
What happens if I add more diluent than the chart shows?
Concentration falls proportionally while total peptide mass stays the same. Adding 4mL to a 10mg vial gives 2.5 mg/mL instead of the 5 mg/mL you would get at 2mL. Very dilute solutions carry more risk from surface adsorption losses and from the working vial outliving its stability window.
Can I add more water later to a vial I already reconstituted?
Arithmetically yes, and the new concentration is total mass divided by total combined volume. Practically it means another needle entry, another agitation event, and a solution whose usable window began at the first reconstitution rather than the second. Deciding the volume before the first entry is the cleaner approach.
Why does the same mg vial give different concentrations on different websites?
Almost always because those sites assume different diluent volumes without stating them. A 5mg vial is 5 mg/mL at 1mL and 1 mg/mL at 5mL, and both figures get published as "the" concentration. Any concentration quoted without its diluent volume is incomplete information.
What is the highest concentration I can make in a 3mL vial?
That depends on both headspace and solubility. A 3mL vial holds slightly under 3mL of liquid in practice, so an 80mg blend reconstituted with 1mL reaches 80 mg/mL. Whether the powder fully dissolves at that concentration is a separate, sequence-dependent question. Slow or incomplete dissolution is the usual sign of having pushed too far.
How do I work out one component's concentration in a blend?
Divide that component's individual mass by the diluent volume, ignoring the other components entirely. In a 70mg GLOW vial reconstituted with 2mL, the 50mg component is 50 ÷ 2 = 25 mg/mL, and each 10mg component is 10 ÷ 2 = 5 mg/mL. The total of 35 mg/mL describes the solution but not any molecule in it. ---
