The apps show a few calculated figures — an estimated-levels curve, a reconstitution and dosing volume, and protein and nutrition targets. This page explains the method and the sources behind each, and — just as importantly — what they are not.
Each time you log a dose, the app treats it as an amount that enters your system at that moment and then decays over time. It adds together the contribution still remaining from every dose you have logged in the window, and plots the running total.
The vertical axis is relative — the whole curve is scaled so its highest point over the window reads 100%. It shows the shape of the rise and fall and the relative difference between peaks and troughs. It is deliberately not expressed in ng/mL or any real concentration unit, because the app has no way to know your true blood level.
We use a one-compartment exponential-decay model with superposition — the standard textbook first approximation for how a substance clears from the body. Each dose decays according to its half-life, and overlapping doses add together:
level(t) = Σ doseᵢ × 0.5 ^ ((t − tᵢ) / t½)
summed over every logged dose i with time tᵢ ≤ t, where t½ is the compound’s half-life.
The final series is then normalised so the peak over the window = 100%.
The half-life for each compound is an approximate literature estimate drawn from published pharmacology and manufacturer data. Reported values often vary widely between sources, studies and individuals, so we use a single representative figure per compound for illustration. A few examples of the values in the model:
| Compound | Approx. half-life used | Class |
|---|---|---|
| Semaglutide | ~7 days | GLP-1 / metabolic |
| Tirzepatide | ~5 days | GLP-1 / metabolic |
| Retatrutide | ~6 days | GLP-1 / metabolic |
| BPC-157 | ~4 hours | Healing / repair |
| TB-500 | ~2–3 days | Healing / repair |
| Ipamorelin | ~2 hours | GH secretagogue |
| CJC-1295 with DAC | ~7 days | GH secretagogue |
Where we don’t hold a reliable half-life for a compound (including many custom compounds you add yourself), the app simply does not draw a curve rather than guess.
This is a measurement converter for research and educational use. It performs standard dilution arithmetic on values you enter — the amount in the vial, the volume of diluent you add, and a target amount. It is not for medical use, does not provide medical advice, and does not recommend, suggest or generate dosages. You acknowledge this before the tool opens.
concentration (mg/mL) = vial amount (mg) ÷ diluent (mL)
volume (mL) = target amount ÷ concentration
Syringe units = volume × the syringe’s units-per-mL. This is the ordinary
concentration-and-volume relationship (concentration = mass ÷ volume) used in any
laboratory dilution — the tool does the arithmetic and never chooses the amount.
Method reference: standard dilution arithmetic. Dividing the mass of solute by the volume
of solvent gives the concentration; the volume required for a given target amount is that
amount divided by the concentration — the elementary relationship
C₁V₁ = C₂V₂ taught in general chemistry.
Fuel sets a daily protein target of 1.6–2.2 g per kilogram of body weight — the range associated in the peer-reviewed literature with maintaining and building lean muscle, and with preserving muscle during weight loss (including on GLP-1 protocols). Calories and the carb/fat split are a balanced default (protein ≈30% of energy) until you set your own numbers. These are general references, not personal dietary or medical advice.
Source: International Society of Sports Nutrition Position Stand: Protein and Exercise (Jäger et al., 2017).