Open almost any profile of an anabolic steroid and you will see two numbers, usually written as a ratio — for example "320:30" or "500:500". These are the anabolic and androgenic ratings, and they are one of the most quoted and most misunderstood figures in the whole subject. This guide explains what they measure, where they came from, and why treating them as precise potency scores will mislead you. It is reference information, not advice to use anything.
The short version: the ratings are a decades-old animal-assay shorthand that is genuinely useful for a first, rough comparison and genuinely unreliable for predicting how a drug behaves in a real training human. Both of those things are true at once.
What the two numbers mean
Every steroid is rated on two axes, each expressed relative to testosterone, which is fixed at 100:
- The anabolic rating estimates tissue-building (muscle-growing) potency.
- The androgenic rating estimates masculinising potency — effects on male reproductive and secondary sexual tissue.
So a compound listed as anabolic 320 / androgenic 30 is, in the original assay, about three times as tissue-building as testosterone but far less androgenic. Testosterone by definition scores 100:100.
Where the numbers actually come from
This is the part most people never learn. The classic ratings come from a rat bioassay developed in the 1950s, often called the Hershberger assay. The method is roughly this:
- Young male rats are castrated to remove their own testosterone.
- They are given the test compound.
- Researchers weigh two tissues afterward: the levator ani muscle (used as the anabolic readout) and the ventral prostate and seminal vesicles (the androgenic readout).
- The growth of each tissue is compared to what testosterone produces, and scaled against testosterone's 100.
That is the entire basis of the numbers you see quoted as if they were laboratory-grade constants. They are averaged results from castrated rodents measuring two specific organs.
Why they are only a rough guide
Several well-understood problems mean the ratings do not translate cleanly to a human lifting weights:
- Wrong species, wrong tissue: the levator ani is not a typical skeletal muscle and rat physiology is not human physiology. A number that predicts levator ani growth in a rat is a weak proxy for biceps growth in a person.
- Methods disagree: different labs used different protocols (oral versus injected, different vehicles, different timings), so published ratings for the same compound vary widely between sources. There is no single authoritative table.
- They ignore metabolism: the assay does not capture what happens when a drug is metabolised in humans — for instance, how testosterone converts to the more androgenic DHT in skin and scalp, which drives real-world hair loss and acne that the raw number does not predict.
- They ignore aromatisation and other pathways: whether a compound converts to estrogen, how it affects cholesterol, its effect on mood or blood pressure — none of this is in the ratio.
- Same number, different experience: two compounds with similar ratings can feel and behave completely differently in practice.
A worked example
Consider a few familiar compounds and their commonly cited ratings:
- Testosterone: 100 / 100 (the reference point).
- Oxandrolone: often quoted around 322-630 / 24, i.e. strongly anabolic and mildly androgenic on paper.
- Nandrolone (as in nandrolone-decanoate): roughly 125 / 37.
- Stanozolol: roughly 320 / 30.
- Trenbolone (as in trenbolone-acetate): often quoted around 500 / 500.
On ratings alone, oxandrolone looks like an almost pure muscle-builder. In reality it is an oral 17-alpha-alkylated compound with its own liver and cholesterol costs that the ratio says nothing about. Trenbolone's 500/500 correctly signals it is powerful, but the number badly undersells how harsh the real-world side-effect profile is. The ratios rank-order intensity loosely; they do not describe the lived experience.
How to use them sensibly
The ratings are best treated as a first-glance sorting tool, not a dosing calculator:
- Use them to get a rough sense of whether a compound leans more anabolic or more androgenic.
- Do not use them to calculate "equivalent doses" between drugs — that is not what the assay supports.
- Always read the compound's actual human pharmacology (aromatisation, DHT conversion, hepatotoxicity, cardiovascular effects) rather than inferring it from two numbers.
Bottom line
The anabolic:androgenic rating is a 1950s rat-assay shorthand, scaled against testosterone at 100, that measures two rodent organs and nothing else. It is a legitimately handy way to rank compounds at a glance and a legitimately poor way to predict how a drug will behave in your body. Respect it as a rough guide, and never mistake it for a precise measure of potency or safety.