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Steroid ester calculator
250 mg of testosterone enanthate is not 250 mg of testosterone. Part of every milligram is the ester chain that slows the release, which is counted in the number on the vial. This works out what you actually deliver, then what the same dose looks like in another ester.
Read this first. Anabolic-androgenic steroids are controlled substances in most countries and are prescription-only where they are legal at all.
Same hormone, other esters
| Ester | Active share | Dose for the same hormone | Half-life |
|---|
Matching the hormone delivered does not match the curve. A short ester delivering the same weekly milligrams does it in sharp peaks, a long one in a flat line. That difference is usually why people switch.
What the ester actually is
It is a chain attached to the hormone to slow its release. Raw testosterone injected into muscle is gone within hours. Attaching a fatty acid chain makes the molecule oil-soluble, so it sits in the injection depot and is cleaved off slowly by enzymes in the blood. The longer the chain, the slower the release and the longer the half-life.
That chain is counted in your dose. Vials are labeled with the mass of the whole esterified molecule, so part of every milligram is chain. Testosterone propionate is about 83% testosterone by weight. Enanthate is about 72%. Undecanoate is around 65%. Nothing is wrong with the label, it is simply not measuring what people assume it measures.
This is why ester switches go wrong. Moving from 100 mg of propionate to 100 mg of enanthate is a cut of roughly 13% in delivered hormone, on top of a completely different release curve. People change ester, keep the number, feel different and blame the compound. The number was never the same number.
Blends make it worse, not better. A blend labeled 250 mg is four esters at four different fractions releasing on four different curves. The delivered hormone is a weighted average and the curve is a sum, which is why blends are difficult to titrate and difficult to interpret from bloodwork.
Common questions
How much actual testosterone is in 250 mg of testosterone enanthate?
About 180 mg. The enanthate chain is roughly 28% of the molecule by weight, so 250 mg of the esterified compound delivers around 180 mg of testosterone once the ester is cleaved off in the blood.
Why is 100 mg of propionate not the same as 100 mg of enanthate?
Propionate carries a shorter chain, so it is about 83% testosterone against enanthate's 72%. The same 100 mg on the label delivers about 83 mg of hormone as propionate and about 72 mg as enanthate, a difference of roughly 13% before the release curves are even considered.
Which testosterone ester delivers the most hormone per milligram?
Of the injectables in common use, propionate. Its chain is the shortest, so the least of each milligram is packaging. Suspension is testosterone with no ester at all and delivers everything, at the cost of a half-life measured in hours.
Does a higher active fraction make an ester better?
No. It only means you need fewer milligrams for the same hormone, which is trivially handled by changing the number. What actually differs is the release curve. A short ester buys its high active fraction with far more frequent injections.
How do I switch esters without changing my dose?
Work out the active milligrams you currently deliver in a week, then divide by the active fraction of the new ester to get the new weekly number. Then set the injection frequency from the new half-life, because keeping the old schedule with a different ester is the part that usually goes wrong.
Do these fractions apply to compounds other than testosterone?
Yes. The calculator covers nandrolone, trenbolone, boldenone and drostanolone esters too. The arithmetic is identical because it is molecular weight, though comparing across different parent hormones is meaningless since they are not interchangeable at any dose.
What about blends like Sustanon?
A blend is several esters in one vial, so its delivered hormone is a weighted average of their fractions and its curve is the sum of theirs. That is why blends are hard to titrate and hard to read from bloodwork, since a single reading is sitting on several overlapping release profiles.
Related tools
And some things do not wait for a blood draw. Chest pain, breathlessness, coughing blood, or pain and swelling in one calf can be a clot. Yellowing of the eyes or skin, dark urine, or pain under the right ribs points at the liver. A sudden severe headache, one-sided weakness or trouble speaking can be a stroke. New or worsening thoughts of harming yourself count too. Get emergency care the same day. Say what you have been taking.
The arithmetic is the easy half
A plan on a web page is not a record of what you actually did. OptiPin logs every injection against the schedule, tracks the compounds in this calculator and lines your bloodwork up against the weeks it belongs to.
It also models what this page deliberately will not. Serum levels rather than milligrams on board: testosterone in ng/dL calibrated per ester, estradiol in pg/mL including what an aromatase inhibitor does to it, both re-fitted to your own bloodwork instead of a population average. Still estimates. Bloodwork is still the instrument that measures.
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