For research and educational purposes only. Not medical advice.
Calculator formulas: how every pepSmart calculator works
Every pepSmart calculator formula in one place: peptide reconstitution, GLP-1 mg-to-units, half-life, doses per vial, TDEE, and more, each with a worked example.
pepSmart does not hide its math. Every number the calculators return comes from a plain formula you can check by hand, and this page collects all of them in one place with a worked example each. Where a formula deserves a full walkthrough, there is a link to a dedicated page. Where it is a one-liner, the formula is right here.
These are educational reference formulas. They compute equivalents and estimates. They are not a dose recommendation, and none of them replace your own product label or prescriber.
Reconstitution and vial math
Turning a dry vial into a measurable dose, and planning how long a vial lasts.
- Peptide reconstitution (concentration):
concentration (mcg/ml) = vial mass in mcg / water volume in ml. 5 mg in 2 ml is 5,000 mcg / 2 ml = 2,500 mcg/ml. - Open calculator
- Full method and examples
- Syringe draw:
draw (ml) = dose in mcg / concentration; units = draw x 100. 250 mcg at 2,500 mcg/ml is 0.1 ml, or 10 U-100 units. - Open calculator
- Full method and examples
- Reverse reconstitution (water to add):
water (ml) = vial mass in mcg / target concentration in mcg/ml. For 2,500 mcg/ml from a 5 mg vial: 5,000 / 2,500 = 2 ml. - Open calculator
- Doses per vial:
doses per vial = floor(vial mass in mcg / dose in mcg). A 10 mg vial at 500 mcg per dose is floor(10,000 / 500) = 20 doses. - Open calculator
- Reconstituted-vial storage window:
usable-until date = reconstitution date + window days. Refrigerated default is 30 days; frozen default is 60 days. - Open calculator
GLP-1 dose math
Converting weekly milligram doses to and from insulin-syringe units.
- GLP-1 dose to units:
draw (ml) = dose in mg / concentration in mg/ml; units = draw x 100. 0.25 mg from a 2.5 mg/ml vial is 0.1 ml, or 10 units. - Open calculator
- Full method and examples
- Units back to dose:
dose (mg) = (units / 100) x concentration in mg/ml. 40 units from a 5 mg/ml vial is 0.4 ml, or 2 mg. - Open calculator
- Full method and examples
- GLP-1 ramp preview:
each step adds the step size after the set number of weeks, up to the target. 0.25 mg starting, +0.25 every 4 weeks, targets 1 mg over 12 weeks. - Open calculator
Pharmacokinetics
How a single dose clears over time.
- Half-life remaining fraction:
fraction remaining = 0.5 ^ (elapsed time / half-life). At one half-life, 50% remains; at two, 25%. - Open calculator
- Full method and examples
- Near-elimination:
about 95% cleared after 4.32 half-lives. Tirzepatide (about 5-day half-life) is about 95% cleared in ~22 days. - Open calculator
- Full method and examples
Body and weight
Energy needs and weight-change estimates.
- TDEE (Mifflin-St Jeor):
BMR = 10 x kg + 6.25 x cm - 5 x age + s (s is +5 male, -161 female); TDEE = BMR x activity. A 40-year-old, 80 kg, 180 cm male at 1.55 activity is about 2,700 kcal. - Open calculator
- Macros from calories:
grams = calories x percent / kcal-per-gram (protein and carbs 4, fat 9). 30% of 2,000 kcal as protein is 600 / 4 = 150 g. - Open calculator
- Weight to calorie deficit:
about 3,500 kcal per pound (7,700 kcal per kg) of body-mass change. A 500 kcal daily deficit is about 1 lb per week. - Open calculator
- Goal-weight ETA:
weeks = weight to change / weekly rate; date = start + weeks. 10 lb to lose at 1 lb/week is about 10 weeks. - Open calculator
Training and recovery
Strength and conditioning references.
- One-rep max:
Epley: weight x (1 + reps / 30); Brzycki: weight x 36 / (37 - reps). 100 kg for 5 reps is about 117 kg by Epley. - Open calculator
- Heart-rate zones:
max HR = 220 - age; zone bands are percentages of max HR (or heart-rate reserve). At age 40, max HR is about 180 bpm. - Open calculator
- Hydration target:
base water from body weight, plus an activity bonus. Moderate activity adds about 250 ml to the baseline. - Open calculator
Frequently asked questions
- Where do these formulas come from?
- They are the same deterministic formulas the pepSmart calculators run, and they are covered by unit tests. Reconstitution and dose math is plain arithmetic. Half-life values are cited from FDA labels. Fitness formulas use published standards (Mifflin-St Jeor for TDEE, Epley and Brzycki for one-rep max).
- Are these formulas medical advice?
- No. They compute equivalents and estimates for research and educational purposes only. They do not account for your product, your prescriber, or your individual physiology.
- Which formulas have a full walkthrough?
- Peptide reconstitution, GLP-1 dose-to-units conversion, and peptide half-life each have a dedicated page with multiple worked examples, edge cases, and common mistakes. The rest are shown inline here with a link to their live calculator.
For research and educational purposes only. Not medical advice.