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The formula used for calculating the rate of compound release at a given day t is:

Λ * N(t)


Where Λ is the decay constant equal to ln(2)/h, h being the half life of the compound given in days; and N(t) is the half-life equation given by:

(t) = n * e^(-t/Λ)


Where n is the original dose of the compound in mg and t is given in days.

Terminal Half-lives

Compound Half-life
Testosterone Propionate 0.8 days
Tesosterone Phenylpropionate 1.5 days
Testosterone Isocaproate 4.0 days
Testosterone Enanthate 4.5 days
Testosterone Cypionate 5.0 days
Testosterone Decanoate 7.5 days
Testosterone Undecanoate 20.9 days
Trenbolone Acetate 1.0 days
Trenbolone Enanthate 4.5 days
Trenbolone Hexahydrobenzylcarbonate 8.0 days
Masteron Propionate 0.8 days
Masteron Enanthate 4.5 days
Nandrolone Phenylpropionate 1.5 days
Nandrolone Decanoate 7.5 days
Equipoise (Boldenone undecylenate) 14.0 days
Primobolan Oral Route 5 hours
Primobolan Enanthate 4.5 days
Halotestin 9.2 hours
Anadrol 8 - 9 hours
Dianabol 4.5 - 6 hours
Turinabol 16 hours
Winstrol Oral Route 9 hours
Winstrol Depot 1.0 days
Anavar 10.4 - 13.3 hours
Superdrol 8 - 12 hours

These half-lives are approximations, and may vary slightly depending on injection site, carrier oil, and other factors.

Note: A different list of half-lives is often copy and pasted on various sites, claiming that, for example, the half-life for the propionate ester is 4.5 days and that the half-life for the enanthate ester is 10.5 days. This list is incorrect, and is the result of flawed calculations many years ago. See the "References" section for more information.


Active Dose

Injectable steroids are typically bound by esters, which comprise a portion of the steroid's weight. Because of this, 100mg of, for example, testosterone enanthate does not equate to 100mg of pure testosterone. In this case, there is only 70mg of testosterone being injected, and the remaining 30mg is the enanthate ester. This is taken into account when plotting cycles on this site, as different esters have different weights. Listed below is the percentages of the actual hormones for different steroid and ester combinations:

Compound Active Dose
Testosterone Propionate 80%
Testosterone Phenylpropionate 66%
Testosterone Isocaproate 72%
Testosterone Enanthate 70%
Testosterone Cypionate 69%
Testosterone Decanoate 62%
Testosterone Undecanoate 61%
Trenbolone Acetate 87%
Trenbolone Enanthate 70%
Trenbolone Hexahydrobenzylcarbonate 66%
Masterone Propionate 80%
Masterone Enanthate 70%
Nandrolone Phenylpropionate 67%
Nandrolone Decanoate 64%
Equipoise (Boldenone) 61%
Primobolan Oral 100%
Primobolan Depot 70%
Halotestin 100%
Anadrol 100%
Dianabol 100%
Turinabol 100%
Winstrol Oral 100%
Winstrol Depot 87%
Anavar 100%
Superdrol 100%

References


Behre HM, Nieschlag E. 1998 Comparative pharmacokinetics of testosterone esters. In: Nieschlag E, Behre HM, eds. Testosterone: Action, Deficiency, Substitution, ed 2. Berlin: Springer-Verlag; 329–348.



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