Peptide Dosage Calculator: How to Calculate Your Exact Dose

Accurate peptide dosing is the foundation of reliable research. Whether you’re conducting studies with BPC-157, semaglutide, tirzepatide, or any other research peptide, getting your dose exactly right matters — even small errors compound over multi-week protocols and can invalidate your results.

This guide explains the math behind peptide dosing, walks through worked examples with real numbers, shows you how to read insulin syringes correctly, and covers every edge case you might encounter. Or, skip the math entirely and use our free peptide dosage calculator.

Why Accurate Dosing Matters in Research

Peptide research demands precision for several critical reasons:

• Dose-response curves are steep — small changes in concentration can produce significantly different outcomes in research models
• Reproducibility requires consistent dosing across experiments — if you can’t reproduce your doses, you can’t reproduce your results
• Cost efficiency — research peptides are expensive; wasting product through calculation errors adds up quickly across a multi-week protocol
• Safety — while these are research compounds, accurate dosing minimizes variables and ensures protocols are followed correctly
• Publication quality — any research intended for publication must demonstrate precise methodology, including exact dosing

A 10% error on a 250 mcg dose means you’re administering anywhere from 225 to 275 mcg. Over a 30-day research protocol with daily dosing, that variance compounds significantly and can skew results beyond acceptable margins.

The Cost of Dosing Errors

Consider a practical example: you’re running a 4-week BPC-157 study with a 5mg vial reconstituted in 2 mL BAC water (2,500 mcg/mL). If you miscalculate and draw 12 units instead of 10 units for each 250 mcg dose, you’re actually administering 300 mcg per dose — 20% more than intended. Over 28 daily doses, you’ll exhaust the vial 5 doses early and your dose-response data will be based on an incorrect dose.

The Core Formula

Peptide dosing involves three simple calculations performed in sequence. Understanding these three steps means you can dose any peptide, any vial size, any syringe — without needing a calculator (though we still recommend using ours to double-check).

Step 1: Calculate Concentration

After reconstitution, your solution has a specific concentration:

Concentration (mg/mL) = Peptide Amount (mg) ÷ Solvent Volume (mL)

Example: 5 mg peptide reconstituted with 2 mL bacteriostatic water:

• 5 ÷ 2 = 2.5 mg/mL
• This equals 2,500 mcg/mL (multiply by 1,000 to convert mg to mcg)

Step 2: Calculate Volume to Draw

Determine how much liquid contains your desired dose:

Volume (mL) = Desired Dose (mcg) ÷ Concentration (mcg/mL)

Example: You want 250 mcg from a 2,500 mcg/mL solution:

• 250 ÷ 2,500 = 0.1 mL

Step 3: Convert to Syringe Units

Insulin syringes are marked in “units” — convert your mL to units:

Syringe Units = Volume (mL) × Units per mL

Important: All standard U-100 insulin syringes have 100 units per mL, regardless of their total capacity. The difference is just how much total volume they can hold.

Example: Drawing 0.1 mL on any insulin syringe:

• 0.1 × 100 = 10 units

So for our example: draw to the 10 unit mark on your insulin syringe for a 250 mcg dose.

The Combined Formula

You can combine all three steps into a single equation:

Syringe Units = (Desired Dose in mcg × Solvent Volume in mL × 100) ÷ (Peptide Amount in mcg)

For 250 mcg from a 5mg vial with 2 mL solvent:

• (250 × 2 × 100) ÷ 5,000 = 50,000 ÷ 5,000 = 10 units

Worked Examples

Example 1: BPC-157 (Common Setup)

• Vial: 5 mg BPC-157
• Solvent: 2 mL bacteriostatic water
• Desired dose: 250 mcg
• Syringe: 1 mL (100 unit)

Calculation:

1. Concentration: 5 mg ÷ 2 mL = 2.5 mg/mL = 2,500 mcg/mL
2. Volume: 250 ÷ 2,500 = 0.1 mL
3. Units: 0.1 × 100 = 10 units
4. Doses per vial: 5,000 mcg ÷ 250 mcg = 20 doses

At one dose per day, this vial lasts 20 days — well within the 28-day BAC water stability window. Read our full BPC-157 dosing guide for more details.

Example 2: Semaglutide (Starting Dose)

• Vial: 3 mg semaglutide
• Solvent: 3 mL bacteriostatic water
• Desired dose: 250 mcg (0.25 mg)
• Syringe: 0.5 mL (50 unit)

Calculation:

1. Concentration: 3 mg ÷ 3 mL = 1 mg/mL = 1,000 mcg/mL
2. Volume: 250 ÷ 1,000 = 0.25 mL
3. Units: 0.25 × 100 = 25 units (on a 50-unit syringe, this is the halfway mark)
4. Doses per vial: 3,000 mcg ÷ 250 mcg = 12 doses (12 weeks at once-weekly dosing)

For complete semaglutide dosing schedules, see our semaglutide reconstitution guide.

Example 3: Tirzepatide (Higher Dose)

• Vial: 5 mg tirzepatide
• Solvent: 2 mL bacteriostatic water
• Desired dose: 2,500 mcg (2.5 mg)
• Syringe: 1 mL (100 unit)

Calculation:

1. Concentration: 5 mg ÷ 2 mL = 2.5 mg/mL = 2,500 mcg/mL
2. Volume: 2,500 ÷ 2,500 = 1.0 mL
3. Units: 1.0 × 100 = 100 units (full syringe)
4. Doses per vial: 5,000 mcg ÷ 2,500 mcg = 2 doses

Tip: When a dose requires a full syringe or more, consider using less solvent during reconstitution to increase concentration, or split the dose across multiple draws.

Example 4: Small Dose with Small Syringe

• Vial: 5 mg peptide
• Solvent: 1 mL bacteriostatic water
• Desired dose: 100 mcg
• Syringe: 0.3 mL (30 unit)

Calculation:

1. Concentration: 5 mg ÷ 1 mL = 5 mg/mL = 5,000 mcg/mL
2. Volume: 100 ÷ 5,000 = 0.02 mL
3. Units: 0.02 × 100 = 2 units

⚠️ Warning: Drawing only 2 units is very difficult to measure accurately. The margin of error at this volume can be 25-50%. Consider using more solvent (e.g., 2 mL instead of 1 mL) to double the volume to 4 units, or use 5 mL to get a comfortable 10 units.

Example 5: Ipamorelin (Moderate Dose)

• Vial: 5 mg ipamorelin
• Solvent: 2.5 mL bacteriostatic water
• Desired dose: 200 mcg
• Syringe: 0.5 mL (50 unit)

Calculation:

1. Concentration: 5 mg ÷ 2.5 mL = 2 mg/mL = 2,000 mcg/mL
2. Volume: 200 ÷ 2,000 = 0.1 mL
3. Units: 0.1 × 100 = 10 units
4. Doses per vial: 5,000 ÷ 200 = 25 doses

Example 6: PT-141 (Larger Vial)

• Vial: 10 mg PT-141
• Solvent: 2 mL bacteriostatic water
• Desired dose: 1,000 mcg (1 mg)
• Syringe: 1 mL (100 unit)

Calculation:

1. Concentration: 10 mg ÷ 2 mL = 5 mg/mL = 5,000 mcg/mL
2. Volume: 1,000 ÷ 5,000 = 0.2 mL
3. Units: 0.2 × 100 = 20 units
4. Doses per vial: 10,000 ÷ 1,000 = 10 doses

Use our calculator to instantly check any combination — it warns you when volumes are too small for accurate reading and suggests better solvent volumes.

How to Read an Insulin Syringe

Understanding syringe markings is crucial for accurate dosing. Misreading a syringe by even one tick mark can significantly alter your dose.

1 mL (100 Unit) Syringe

• Major lines every 10 units (labeled: 10, 20, 30… 100)
• Minor lines every 2 units (5 tick marks between major lines)
• Each minor tick = 2 units = 0.02 mL
• Precision: ± 2 units (± 0.02 mL)
• Best for doses requiring 20+ units

0.5 mL (50 Unit) Syringe

• Major lines every 5 units (labeled: 5, 10, 15… 50)
• Minor lines every 1 unit
• Each minor tick = 1 unit = 0.01 mL
• Precision: ± 1 unit (± 0.01 mL)
• Best for most peptide dosing — highest practical resolution

0.3 mL (30 Unit) Syringe

• Major lines every 5 units (labeled: 5, 10, 15… 30)
• Minor lines every 1 unit (some syringes show half-unit marks)
• Each minor tick = 1 unit = 0.01 mL (or 0.5 units on half-unit syringes)
• Ideal for very small doses under 15 units

Reading Tips

• Hold the syringe at eye level with the markings facing you
• Read from the top of the plunger (the flat edge closest to the needle), not the bottom
• The meniscus (curved liquid surface) should sit right at your target line
• If between two lines, push the plunger slightly to reach the nearest mark rather than estimating
• Practice with plain water before working with peptides — it’s free and builds confidence
• Good lighting matters — use a desk lamp or work near a window

For a deeper dive, see our insulin syringe units explained guide.

Which Syringe Should You Use?

General rule: Use the smallest syringe that can comfortably hold your dose. Smaller syringes have finer markings and higher precision.

Understanding Units, IU, and mL

A common source of confusion in peptide dosing is the difference between various measurement units. Getting these wrong can result in dramatic dosing errors.

Syringe Units (Not What You Think)

• Not International Units (IU) — these are simply volume markings on insulin syringes
• 100 units = 1 mL on a standard U-100 insulin syringe
• Think of them as tick marks measuring volume, nothing more
• When peptide guides say “draw 10 units,” they mean the 10-unit mark on the syringe

International Units (IU)

• A biological measurement of potency, not volume
• Used for HCG, HGH, HMG, and certain other peptides and hormones
• Different peptides have different IU-to-mcg ratios
• Example: HGH is approximately 3 IU per mg (so 1 IU ≈ 333 mcg)
• Example: HCG has its own IU-to-mass relationship that varies by preparation
• IU must be converted to mcg/mg before using a standard dosing calculator

Micrograms (mcg) and Milligrams (mg)

• 1 mg = 1,000 mcg — this is the most important conversion to remember
• Most peptide doses are expressed in mcg (e.g., 250 mcg BPC-157)
• Vial sizes are expressed in mg (e.g., 5 mg vial)
• Some literature uses “μg” instead of “mcg” — they mean the same thing

Nanomoles (nmol) and Other Units

• Some research papers express peptide doses in nmol (nanomoles)
• Converting nmol to mcg requires the peptide’s molecular weight
• Formula: mcg = nmol × (molecular weight ÷ 1,000)
• This is rarely needed for practical dosing but important for reading clinical literature

Optimizing Your Solvent Volume

Choosing how much bacteriostatic water to add during reconstitution directly affects your dosing experience. Here’s how to optimize:

The Sweet Spot

Your goal is to choose a solvent volume that makes your target dose fall between 5 and 50 units on your syringe:

• Below 5 units: Too small to measure accurately — increase solvent volume
• 5-15 units: Good precision with a 0.3 mL or 0.5 mL syringe
• 15-50 units: Ideal range for most applications
• Above 50 units: Consider less solvent or a larger syringe

Quick Reference Table

Doses Per Vial Calculator

Knowing how many doses you can get from a single vial helps with budgeting, planning, and determining when to reconstitute new vials:

Doses per vial = Total Peptide (mcg) ÷ Dose per use (mcg)

Our calculator automatically shows doses per vial for any peptide and dose combination.

Planning Your Research Protocol

When planning a multi-week study, calculate total vials needed:

Total vials = (Doses per week × Number of weeks) ÷ Doses per vial

Example: 4-week BPC-157 study, 250 mcg twice daily:

• Doses needed: 2 × 28 = 56 doses
• Doses per 5mg vial: 20
• Vials needed: 56 ÷ 20 = 2.8 → 3 vials

Remember that reconstituted vials expire after 28-30 days. Time your reconstitutions so you don’t reconstitute a vial you can’t finish within the stability window.

Common Dosing Mistakes

Confusing mg and mcg

A 250 mcg dose is very different from 250 mg (which would be the contents of 50 five-milligram vials). Always double-check your units. This is the single most dangerous calculation error in peptide research. When in doubt: most individual peptide doses are in the microgram (mcg) range.

Using the Wrong Syringe for Calculations

If you calculate for a 100-unit syringe but use a 50-unit syringe, you won’t draw twice the dose (since both are U-100), but the markings will look different and can cause confusion. Always verify which syringe you’re using and understand its tick marks.

Not Accounting for Dead Space

Insulin syringes have a small amount of “dead space” (0.5-2 units) in the hub where liquid remains after the plunger is fully depressed. For most research purposes, this is negligible. For very precise work or very expensive peptides, note that you may lose 1-2% of each dose to dead space. Low dead space (LDS) syringes are available and minimize this issue.

Forgetting to Account for Multiple Draws

Each time you insert a needle into a vial, a tiny amount of liquid is lost in the needle hub and through evaporation. Over many draws from a single vial, this adds up. In practice, you may get 1-2 fewer doses than calculated. Budget accordingly.

Rounding Errors

When calculations give you fractional units (like 7.5 units), round to the nearest whole unit marking on your syringe. A 0.5-unit rounding error on a 250 mcg dose is only a ~1.5% variance — well within acceptable range for most research protocols.

Calculation Drift Over Protocol Duration

If you slightly overdraw each dose (e.g., 11 units instead of 10), you’ll run out of peptide before the protocol ends. Track your remaining volume and recalculate periodically to ensure you have enough product to complete the study.

Frequently Asked Questions

How do I know what dose to use?

Dosing protocols vary by peptide and research application. Published literature, clinical trial data, and manufacturer guidelines provide starting points. Our calculator includes typical dosing ranges for popular peptides as reference points.

What if my calculated dose exceeds the syringe capacity?

Either use a larger syringe (move from 0.5 mL to 1.0 mL) or increase your solution’s concentration by adding less solvent during reconstitution. Our calculator will warn you if a dose exceeds syringe capacity.

Can I mix two peptides in the same syringe?

Some researchers combine compatible peptides (e.g., CJC-1295 and Ipamorelin) in a single syringe to reduce injection volume. However, this requires knowing that the peptides are chemically compatible and won’t interact or degrade each other. When in doubt, administer separately.

How do I dose peptides measured in IU?

Peptides like HCG and HGH use International Units. The IU-to-mcg conversion is specific to each peptide and preparation. For HGH, approximately 1 mg = 3 IU. For HCG, the conversion varies by preparation. Our calculator handles IU-based peptides with built-in conversion factors.

What’s the most accurate way to measure small doses?

Use a 0.3 mL (30 unit) syringe for doses under 10 units — these have the finest markings and lowest margin of error. If your dose requires less than 3 units, strongly consider adding more solvent to your peptide vial to lower the concentration and increase the draw volume.

Does the syringe needle gauge affect dosing accuracy?

The needle gauge (thickness) doesn’t affect the volume measurement. However, thicker needles (lower gauge numbers) are slightly easier to draw with but create larger puncture holes in vial stoppers. For peptide dosing, 29-31 gauge needles are standard and work well.

How do I handle dose titration (gradually increasing doses)?

Many peptide protocols involve starting at a lower dose and increasing over time (common with semaglutide and tirzepatide). Calculate each dose level in advance and write down the syringe units for each step. Our calculator lets you quickly recalculate for different dose levels without changing your reconstitution.

Can I use a volumetric pipette instead of a syringe?

For reconstitution, pipettes can work but are generally less practical than syringes for peptide research. For dosing (subcutaneous administration), insulin syringes are the standard tool. Pipettes are more appropriate for in-vitro research where the peptide is being added to cell cultures or assay plates.

Quick Reference: The 3-Step Formula

1. Concentration = Peptide (mg) ÷ Solvent (mL)
2. Volume to draw = Desired dose (mcg) ÷ Concentration (mcg/mL)
3. Syringe units = Volume (mL) × 100

Or bookmark our peptide dosage calculator and let it do the work for you — with visual syringe graphics, 30+ peptide presets, and instant results.

For accurate dosing, start with quality peptides. Trusted suppliers like Chameleon Peptides provide accurate vial amounts verified by third-party testing, so your calculations start from a reliable baseline.