Different esters of the same steroid don’t magically change the core effects of the hormone, they change how fast it hits, how long it hangs around, and how much actual active hormone you get per milligram. Most of the “this ester gives more water” or “that ester gives more striations” talk comes down to release curve and blood level timing, not some special property of the ester itself.​

What esters really do

An ester is just a chemical tail attached to the base hormone to slow its release from the injection depot.

• Short esters (like acetate, propionate) are more water‑soluble and are hydrolysed faster, so they spike and clear more quickly.
• Long esters (like enanthate, cypionate, decanoate, undecanoate) release the hormone more slowly, leading to smoother, longer curves and less frequent injections.​

Crucially:

• Aromatase and 5‑alpha‑reductase act on the free hormone, not on the ester. The ester must be cleaved first, then that same testosterone (or nandrolone, tren, etc.) is what converts to estrogen or DHT.​
• Given the same average blood level of free hormone over time, different esters do not change its inherent ability to aromatise or build muscle. Testosterone is testosterone; tren is tren.​

Differences people feel usually come from how quickly levels rise and fall, and how well or badly they manage those swings.

Water retention and gyno: timing, not magic

Water retention and estrogen‑type sides track with:

• Peak blood levels of free testosterone and resulting estradiol.
• How steep and frequent those peaks are.

Examples:

• Testosterone suspension (no ester) has a very short active life (around an hour or so) and produces very sharp peaks, which is why it is notorious for bloat and gyno when dose and AI are not controlled.​
• Short esters (propionate, acetate) hit faster and peak earlier than long esters, so people sometimes feel sides more abruptly.
• Long esters (enanthate, cypionate, undecanoate) build up more slowly and produce flatter curves, which can feel “smoother” with fewer acute swings.​

At the same average testosterone level, though, the rate of aromatisation and water retention potential is essentially the same, there’s no biochemical mechanism that would make testosterone enanthate inherently more “watery” than the same amount of testosterone cypionate once in the blood.​

Active hormone per 100 mg

Because the ester adds weight, not all “100 mg/ml” vials contain the same amount of actual hormone.

Approximate active hormone per 100 mg finished product (typical values):​

• Testosterone base: 100 mg
• Testosterone acetate: ~83 mg
• Testosterone propionate: ~80 mg
• Testosterone enanthate: ~70–72 mg
• Testosterone cypionate: ~69–70 mg
• Testosterone decanoate: ~62–65 mg
• Testosterone undecanoate: ~61 mg

Similar patterns apply to other compounds (boldenone, nandrolone, trenbolone, methenolone, etc.): the longer the ester, the lower the percentage of active hormone per 100 mg. That’s why, on paper, 200 mg/ml of one ester is not exactly the same “bang for the buck” as 200 mg/ml of another, enanthate will give you slightly more test base per ml than cypionate, for example.​

Half‑life and feel

Typical active half‑lives (ballpark ranges):​

• Suspension: within hours
• Acetate/propionate: ~1–3 days (depending on source and formulation)
• Enanthate: ~5–10 days
• Cypionate: ~7–12 days
• Decanoate/undecanoate: ~2–3+ weeks

So:

• Enanthate will generally release its testosterone slightly faster and peak slightly sooner than cypionate.
• Cypionate hangs a little longer, so changes (good and bad) may come on a touch slower.

Side effects that differ between enanthate and cypionate are almost always about these kinetics: how quickly levels climb, how high the peaks are between injections, and how often you pin. The molecule doing the work once the ester is cleaved is the same.​

Why people swear one ester “gives more cuts”

A lot of anecdote like “prop makes me dry, enanthate makes me smooth” can be explained by:

• Short esters being used more often in cutting phases where diet, cardio, and AI use are tighter.
• Long esters being used more in bulk phases with higher calories, more sodium, and looser estrogen control.

Blame the context and blood‑level patterns, not the ester itself. Given identical nutrition, AI management, and steady hormone levels, you won’t suddenly get “inner chest striations” from one ester and bloat from another; the base hormone drives the look, the ester just dictates the ride.