Peptide research requires precise calculations at every stage — from synthesis to reconstitution to dosing. This guide covers the essential calculators, their applications, and the underlying mathematics.
Calculator Primary Use Key Input Reconstitution Diluent volume Mass + target concentration Dose conversion Dose ↔ volume Concentration + target dose Molecular weight Molar calculations Amino acid sequence Insulin syringe Units ↔ mL Syringe type + volume Molarity Moles ↔ mass Molecular weight + concentration Dilution Concentration adjustment Initial + target concentration
Volume (mL) = Mass (mg) ÷ Desired Concentration (mg/mL)
Mass Target Concentration Volume Needed 5 mg 1 mg/mL 5 mL 2 mg 0.5 mg/mL 4 mL 10 mg 2 mg/mL 5 mL 3 mg 3 mg/mL 1 mL
Preparing lyophilized peptide vials
Calculating bacteriostatic water volumes
Planning multi-dose vial preparations
Volume (mL) = Dose (mg) ÷ Concentration (mg/mL)
Dose Volume U-100 Units 50 µg 0.05 mL 5 units 100 µg 0.10 mL 10 units 150 µg 0.15 mL 15 units 200 µg 0.20 mL 20 units 250 µg 0.25 mL 25 units 500 µg 0.50 mL 50 units 1000 µg 1.00 mL 100 units
Determining injection volume for a target dose
Converting between µg and mL
Planning injection schedules
Sum the residue masses of each amino acid, then add water (18.015 Da) for the C-terminus.
AA 1-letter Mass (Da) Alanine A 71.08 Arginine R 156.19 Asparagine N 114.10 Aspartic acid D 115.09 Cysteine C 103.14 Glutamic acid E 129.12 Glutamine Q 128.13 Glycine G 57.05 Histidine H 137.14 Isoleucine I 113.16 Leucine L 113.16 Lysine K 128.17 Methionine M 131.20 Phenylalanine F 147.18 Proline P 97.12 Serine S 87.08 Threonine T 101.10 Tryptophan W 186.21 Tyrosine Y 163.18 Valine V 99.13
G(57.05) + E(129.12) + P(97.12) + P(97.12) + P(97.12) + G(57.05) + K(128.17) +
P(97.12) + A(71.08) + D(115.09) + D(115.09) + A(71.08) + G(57.05) + L(113.16) +
V(99.13) + H₂O(18.02) = 1,419.5 Da
Verifying peptide identity
Molar concentration calculations
Stoichiometric planning
Molarity (M) = Concentration (g/L) ÷ Molecular Weight (g/mol)
Concentration (g/L) = Molarity (mol/L) × Molecular Weight (g/mol)
Concentration Molarity 1 mg/mL 0.704 mM 0.5 mg/mL 0.352 mM 2 mg/mL 1.409 mM
Converting between mass and molar concentrations
Comparing peptide concentrations across different MW
Planning molar-ratio experiments
Where:
C₁ = Initial concentration
V₁ = Initial volume
C₂ = Final concentration
V₂ = Final volume
Dilute 10 mL of 2 mg/mL peptide to 0.5 mg/mL:
V₂ = (C₁V₁) ÷ C₂ = (2 × 10) ÷ 0.5 = 40 mL
Add 30 mL diluent to 10 mL stock solution.
Preparing working solutions from stock
Creating dose-response dilution series
Adjusting concentration for compatibility
mL Units 0.05 5 0.10 10 0.20 20 0.25 25 0.50 50 1.00 100
Translating reconstitution volumes to injection units
Verifying syringe measurements
Factor Impact Mitigation Temperature Degradation doubles per 10°C rise Store at 2–8°C pH Extremes accelerate hydrolysis Buffer at optimal pH Oxidation Methionine, cysteine sensitive Nitrogen overlay, antioxidants Aggregation Loss of bioactivity Avoid agitation Light Photodegradation Amber vials, dark storage
Condition Lyophilized Reconstituted 2–8°C 12–24 months 14–30 days −20°C 24+ months Do not freeze Room temp Days–weeks Use same day
Planning storage and handling
Estimating remaining potency
Designing stability studies
From To Multiply by g mg 1000 mg µg 1000 mL µL 1000 M mM 1000 mM µM 1000 Da kDa 0.001
PMC. “Peptide Calculator Tools for Research Applications.” NIH 2024.
IUPAC. “Quantities, Units and Symbols in Physical Chemistry.” IUPAC 2023.
