Peptide Blend Math: What Each Component Delivers
How to calculate a peptide blend: why one draw carries every peptide in the vial at a fixed ratio, the one formula that matters, and three worked examples.
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Blog
Guides, notes and background reading.
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How to Read a Peptide Certificate of Analysis
A field guide to the peptide certificate of analysis: what HPLC purity, assay, net peptide content and counter-ion lines mean, with the arithmetic that follows.
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How Reverse Peptide Calculations Work
A reverse calculation starts from the answer and works back to the input: from a target concentration or a syringe reading, to the volume of diluent to add.
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How to Calculate Doses per Vial
Doses per vial is the vial mass divided by the amount per dose. Why the theoretical count is always optimistic, and which losses account for the difference.
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Why International Units Cannot Be Converted to mg
An IU measures biological activity, not mass. There is no universal IU to mg conversion, because the factor belongs to a specific substance and often a specific batch.
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Molarity versus Mass Concentration
mg per mL and mM are different measurements of the same thing. What the difference is, why they diverge by the molecular weight, and when each one is the right unit.
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What Molecular Weight Means for Peptide Calculations
Molecular weight is the bridge between mass and moles. Why it is needed, why average differs from monoisotopic, and where it enters every peptide calculation.
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How Peptide Cost Per Dose Calculations Work
Cost per dose is the only unit that compares two products fairly. What goes into it, what it leaves out, and why cost per milligram is not comparable across peptides.
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How Rounding Affects Small-Volume Peptide Calculations
Rounding the concentration puts every later step out by the same proportion. Why small draw volumes magnify that error, and when a rounded reading is harmless.
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A Practical Guide to Peptide Unit Conversions
The peptide unit conversion guide: crossing mass and mole units needs a molecular weight; a worked mg-to-mM example shows which calculator handles each step.
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Peptide Net Charge and pH: Henderson-Hasselbalch
Peptide net charge at any pH, calculated with the Henderson-Hasselbalch equation: the per-group formula behind net charge and isoelectric point results.
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Steady-State Accumulation Factor, the Math
The steady state accumulation factor formula, R = 1 / (1 - e^-k*tau), explained: how repeated dosing intervals build toward a fixed multiple of one dose.
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First-Order Elimination and Half-Life, the Math
First-order elimination half-life math explained: the A(t) = A0 x e^-kt decay equation, how k and half-life relate, and how to solve for time or amount.
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A Planning Guide to Serial Dilution
Serial dilution formula: concentration at step i = initial concentration / (dilution factor ^ i); how to plan step volumes versus a single C1V1 dilution.
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Beer-Lambert Law: Peptide Concentration From Absorbance
Beer-Lambert law for peptide concentration: the A = e x c x l formula, how to solve it for concentration or path length, and how e comes from Trp, Tyr, Cys.
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GRAVY Score and Kyte-Doolittle Hydrophobicity
GRAVY score formula explained: how the Kyte-Doolittle hydrophobicity scale averages over a sequence, plus how it compares to aliphatic index and Boman index.
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Peptide Isoelectric Point (pI), Explained
How a peptide isoelectric point (pI) is calculated: the bisection search that finds where net charge crosses zero, on the same Bjellqvist pKa scale as ExPASy.
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Monoisotopic Mass vs. Average Molecular Weight
Monoisotopic mass vs average molecular weight: why they diverge as a peptide sequence gets longer, and the exact formula each calculator uses to compute it.
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How to Calculate Peptide Molecular Weight From a Sequence
The sum-of-residue-masses method for finding a peptide molecular weight from its amino acid sequence, and how it connects to mass, mole and molarity calculators.
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How many units is 0.25 mg of semaglutide?
0.25 mg of semaglutide is 10 units at 2.5 mg/mL, 5 units at 5 mg/mL, or 2.5 units at 10 mg/mL: worked examples for common compounded vial concentrations.
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How to reconstitute a peptide vial: the arithmetic
How to reconstitute a peptide vial: concentration = peptide mass / water added, then draw volume = dose / concentration, converted into a syringe reading.
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How to convert mg to units on an insulin syringe
The mg to units formula: units = (dose in mg / concentration in mg per mL) x units per mL of the syringe, worked through with checkable examples.
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Reading a GLP-1 titration schedule without misreading it
How to read a GLP-1 titration schedule: semaglutide starts at 0.25 mg weekly, tirzepatide at 2.5 mg weekly, each held four weeks before the labelled increase.
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Tirzepatide mg to units: the exact arithmetic
Tirzepatide mg to units: draw volume = dose / concentration, units = draw volume x 100 on U-100; worked for a 20 mg vial in 2 mL, citing the labelled schedule.
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U-100 and U-40 syringes read the same volume differently
A U-100 barrel is graduated at 100 units per mL and a U-40 barrel at 40, so reading one as the other changes what you drew by two and a half times.
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