One of the most overlooked parts of cycle planning is understanding ester half-lives. The ester attached to a compound doesn’t change its potency — but it does control how long the compound stays active, how often you need to inject, and how long it takes before you can start recovery.
To make this easier, I built a steroid cycle calculator and half-life plotter. It lets you plug in your cycle details and instantly see vial requirements, injection volumes, and an interactive graph of how your levels rise and fall.
What Are Steroid Half-Lives?
Each ester has a different rate at which it’s broken down.
- Short esters (like acetate or propionate) clear fast but need frequent injections.
- Long esters (like decanoate or undecanoate) build up slowly and linger for weeks.
This directly impacts cycle design, injection planning, and recovery timing.
Why Half-Lives Matter for Cycle Planning
- Injection frequency: Short esters = more injections.
- Buildup time: Longer esters = slow start.
- Side effect control: Stable levels = fewer swings in mood, water retention, or estrogen spikes.
PCT timing: Knowing when compounds clear helps prevent starting recovery too early.
Free Steroid Cycle Calculator
Here’s how the tool works:
Enter:
- Compounds you’ll use
- Weekly dose
- Vial concentration and size (Or tablet concentration and tabs/bottle)
- Cycle length
- Injection frequency (Or tablet dosing/per day)
The calculator shows:
- Total vials/bottles needed
- Weekly injection volume (per compound)
- Amount per injection (per compound and total)
- Weekly tablets
- Tablets per dose
- Half-life graph over your full cycle
👉 For more detail and examples, check the full Steroid Cycle Calculator page.
Example: Testosterone Propionate vs Enanthate
When you run the numbers, you’ll see how different the injection planning becomes:
This is both compounds graphed with 3 injections a week, 250mg total.
- Testosterone Propionate → Requires small, frequent injections to stay stable.
- Testosterone Enanthate → Can be maintained with fewer injections but takes longer to clear.
Visualizing this in the graph makes the difference immediately clear.
Final Thoughts
Half-life planning is one of the most important — and most ignored — aspects of cycle design.
This calculator helps visualize it clearly, while also keeping track of injection volumes and vial requirements.
⚠️ Reminder: This tool is for educational purposes only. It is not a recommendation or medical guidance.
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