Ester Calculator · TRT Reference

200mg Testosterone Cypionate
Is Not 200mg of Testosterone

It's approximately 140mg. The ester attached to make the compound injectable adds mass — the labeled dose is the compound weight, not the testosterone weight. Here's the conversion across all major esters.

The Reference Table

Free Testosterone Content by Ester

Cypionate
69.9%
~140mg T per 200mg labeled dose
Enanthate
72.0%
~144mg T per 200mg labeled dose
Propionate
80.4%
~161mg T per 200mg labeled dose
Undecanoate
63.0%
~126mg T per 200mg labeled dose
EsterFree T%100mg dose → actual T200mg dose → actual THalf-life
Testosterone Cypionate69.9%69.9mg139.8mg~8 days
Testosterone Enanthate72.0%72.0mg144.0mg~7 days
Testosterone Propionate80.4%80.4mg160.8mg~2 days
Testosterone Undecanoate (inj)63.0%63.0mg126.0mg~21 days
Testosterone Blend (Sustanon)~72%~72mg~144mgMixed
Testosterone Undecanoate (oral)63.0%63.0mg126.0mg~4 hrs

Free T percentages are molecular weight ratios. Actual bioavailability varies by injection depth, carrier oil, individual metabolism, and injection site. These values represent the theoretical free testosterone content, not necessarily the amount that becomes biologically available.

Why It Matters

Why the Ester Conversion Matters for Your Protocol

When comparing TRT protocols or evaluating dose adjustments, the labeled compound dose can mislead. A protocol calling for 200mg Testosterone Cypionate weekly delivers roughly 140mg of actual testosterone. A protocol using 200mg Testosterone Propionate delivers about 161mg — 15% more actual testosterone at the same labeled dose. If you're switching esters while trying to maintain the same testosterone exposure, the dose needs to account for this difference.

The ester conversion also matters when calculating peak concentration relative to your bloodwork draw timing. The half-life column determines how long the compound stays active and when a mid-cycle draw most accurately represents your stable-state levels. Cypionate at 8 days and Propionate at 2 days require completely different draw windows to capture comparable data.

Protocol's built-in TRT ester calculator handles this math directly. Available free on iOS and Android at protocolapp.health/tools/peptide-calculator.

FAQ

Ester Calculator Questions

Does the ester difference affect my blood test results?
Indirectly yes. The ester determines half-life, which determines how your testosterone levels vary between injections. Long esters (Cypionate, Enanthate) produce lower peak-to-trough variation on weekly dosing. Short esters (Propionate) require more frequent injections to maintain stable levels but give more precise control. The ester also affects when to time your bloodwork draw for a representative steady-state reading.
Why is Testosterone Cypionate the most commonly prescribed ester?
Testosterone Cypionate is the most common TRT ester in the United States primarily for practical reasons: it's been widely manufactured domestically for decades, it's stocked by most compounding pharmacies, and its ~8-day half-life allows once-weekly or twice-weekly dosing. The free testosterone percentage (69.9%) and actual clinical outcomes are comparable to Enanthate — the difference is largely historical and logistical rather than pharmacological.
How do I use this table to adjust my dose when switching esters?
Divide your current labeled dose by your current ester's Free T% to find your target actual testosterone, then divide by the new ester's Free T% to get the equivalent labeled dose. Example: switching from 200mg Cypionate (69.9% → 139.8mg T) to Enanthate: 139.8mg ÷ 0.72 = ~194mg Enanthate to deliver the same testosterone. Always make any dose changes in consultation with your prescribing physician.

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